most shots I'll take at this point are in photo books. Have a large-ish Epson 4990 Perfection 9x12 flatbed I haven't used in quite a while which could be good for this, appreciate the prods above, but of course the driver I have doesn't work with iMac 12.6 and its seems no update... I did keep a five year old iMac for such purpose but at the moment can't get it to fire; if could get it going wonder if that could serve decently via shot uploads and then tweak on the new iMac or if I need a new Epson? Or?

Using a scanner is your best bet for a "production line" setup. This will keep prints flat, there will be no issues with glossy prints and you can make any correction in density, contrast, and saturation in post-processing.

If you prefer to use your camera, especially with prints that won't find in the scanner, my preferred setup is using cross-polarization, that is polarization filters on your ligh and a CPL filter on the lens.

The polarization filters for the ligh are made of acetate and are available for various sources including Rosco. The ones I use are mounted on cardboard with index marks to insure that are placed in the correct direction over the lights. You can use electronic flash, incandescent, or LED light sources in standard reflectors.

I set up a horizontal "copy stand" or easel and place each ligh at 45 degrees. The camera is kept parallel to the prints. Whe the CPL filter is rotated, at one point, all unwanted reflections will be eliminated and contrast and color saturation will be maximized.

You can set up the light to cover the largest prints and leave them at that distance for all the other prints. Once you even out the lighting and establish exposure, you can shoot all of the prints in athe same settings. To insure even lighting, take a meter reading at each corner of the copy surface and move the lights incrementally until all the readigs match. It tasks a bit of setup time but once you establish things the restof the job can move rapidly.

See attached diagrams for the lighting setup. The diagram shows my old setup with a large format camera. Nowadas I use a digital camera fitted with a macro lens. There is a shot of the acetate polarizing filter. The copy stand is not necessary, an easel ledge on the wall or magnetic copy board will do the job.

There is much software available for slide show production that will enable fades, lap dissolves, wipes, etc. as well as the inclusion of a music track.

Having done a number of these shows, I know what a chore it is! Here are some pointers:

> Pre-edit. Before any reproduction of hard copies, separate the ones that work from the ones that don't. It takes a lot of time to copy or scan photos and post-process them for use in a show of some sort.

> Decide what level of quality you are going for. It takes a LOT of work to make things look pristine clean and "like you were just there." For some shows, that's worth it. But for others, simple copies with no editing may work.

> The best reproductions of original prints and printed materials such as books are made with a macro lens and a digital camera. If you have, or create, a "copy stand" setup, you can rapidly record raw files and adjust them in post to crop, straighten, spot, lighten, darken, adjust color, tweak sharpness, etc. In this instance, post-processing will take the longest.

> If you have a PHOTO grade flatbed scanner, capable of generating 16-bit TIFF files, you may also get great results. Your scanner driver software may make use of scanner technology that hides dust and scratches, and may also attempt to "restore" color and tone. However, scan times can be quite long when using those features.

> If you want to copy actual slides or original, black-and-white or color film negatives, read my white paper on how I do it. It's attached as a PDF file download, below.

> The vital principles of copy stand photography:

— Keep the sensor of the camera parallel to the copy stand base.

— Use relatively large light sources centered at 37.5° to 45° above the copy surface, spaced far enough away, EQUALLY, on the left and right sides of the copy board, to provide even illumination. Feather the light to keep exposure within 1/6 of one f/stop across the copy board.

I use a pair of NEEWER 17"x12" LED panels I bought for video production, because they are quite close to daylight color quality and generate almost no heat. But you can use 3200K quartz-halogen incandescents (they're hot and waste energy!), or Type ECA 250-Watt Photoflood bulbs, or PHOTO GRADE, FLICKER FREE CFL or LED bulbs. Just be sure the sources are identical on both sides of the copy stand and that they are reasonably large. You want any specular reflections from embossed or stippled papers to be at the same brightness as the rest of the image. The way you do that is to use light sources that are large, so they "wrap the light" around all the surface irregularities.

— Batch copy by sizes to minimize changes in camera position or magnification. I do all 4x5 and 4x6 inch prints at the same magnification, all 3x3 and 3x5 prints at the same magnification, all 5x5 and 5x7 prints at the same magnification... I set the camera height to get the entire image in the frame, but any wasted space is on the sides, not top and bottom. I rotate in post, when necessary.

— Avoid using glass. I use a couple of 2" strips cut from 8.5x11 inch magnetic sheet material used to make refrigerator magnets. These are heavy enough to hold most prints flat. I place them over the top and bottom edges of prints that curl.

— Remove prints from album pages when possible. If glued, DON'T remove them, but remove the entire page if the album can be disassembled and reassembled somehow. If the album uses sticky wax beads under a sheet of plastic to hold the prints, expect the prints to be deteriorated. You might have to photograph them "as is." This was the worst-conceived album ever manufactured. The best albums — and easiest to work with when doing projects like this — use slip-in, pocketed polypropylene (inert plastic) pages. They're not the prettiest, but they are reasonably priced and archival-safe.

— If you must photograph items in books or albums, do what you can to keep the images parallel to the camera sensor! That usually involves propping up part of the book. It may involve rotating the image 90° so the whole thing is lit properly.

— If you must photograph through glass, try to use polarizing filters on the light sources and the camera lens. Also work in a BLACK room, with a BLACK ceiling, and a BLACK baffle that hides the camera and copy stand components. All of this is to avoid reflections off the glass! Black plastic landscape plastic is your friend... Rub it with a wool sweater to give it a static charge and it acts like a dust magnet to clean the air around your work surfaces. Black Velcro® sheeting is useful to absorb light, too.

— Each time you move the camera, meter a Delta-1 18% Gray Card or a similar gray balance exposure reference tool. Typically, keep your aperture about two or three stops down from wide open (f/6.3 on a 55mm or 60mm Micro Nikkor has always worked for me). Set MANUAL ISO, MANUAL Shutter Speed, MANUAL Aperture, and CUSTOM/MANUAL/PRESET white balance in reference to the gray card.

— I use multi-point AF with great success. It's more accurate than my old, tired eyes and manual focus.

— Record and process raw files. The white balance you took at the camera is stored in the EXIF data of the JPEG preview image stuffed into the raw file, and will prime your post-production software, so you'll get close to perfect reproduction right out of the gate.

I work in Lightroom Classic, which does well over 90% of what I need to make images ready for use. I use all of its tools at one time or another, so I won't do a tutorial on that here. When needed, I send files to Photoshop and back for additional work.

— I produce my actual slide shows as 4K videos, using Final Cut Pro, a Mac-only video editor. FCP allows me to import stills, convert them to video, time them, crop them, pan and zoom them, title them, add special effects, add music, add narration... In short, practically any production tool Ken Burns has used in his shows on PBS is available in Final Cut.

WARNING: 4K video generates HUGE files. Last Spring, I did a 44 minute, 850+ slide show to run in the background of a class reunion dinner. The original edit file in Apple ProRes format was 867 GIGABYTES without sound! I presented a 44 GB export, and posted an 11.5 GB 1080P (2K) version to my private YouTube channel accessible by classmates.

In preparation for video, I size all my images to 3840x2160 pixels (4K standard video resolution). To do that, I use Photoshop to resize and pad canvas. Few, if any, images start as 16:9 aspect ratio, although I do crop many to that aspect ratio in Lightroom Classic. I use Photoshop to create 3840x2160 pixel JPEGs imported into Final Cut Pro for the show. I've attached a few sample images below, after the white paper on camera scanning slides and negatives. These are all from that same 45th year class reunion show mentioned above.

When you say "does a decent job" the question is compared to what ? If you are genuinely satisfied with the output of your printer, That is what counts the most. If you are interested in showing the maximum possible quality available from a camera like a D850, the answer is you can do significantly better.
True large format , wide Gamut photographic printers can make really wonderful and noticeably superior prints in an optimized workflow. Which includes providing an optimized file --usually a 16bit TIFF in the appropriate color space, and density.
Many labs work mostly from JPEGs which limits your color space to sRGB. The D850 files can exceed Adobe RGB.
However it is unlikely that any file you send to a lab will be the best possible file for the way they are set up. That's why people 'soft proof' to dial in an optimized file, or have printers controlled by RIP (Raster image Processor) software like Image Print.
If you are serious about getting the best quality, pick a lab that Accepts TIFFS in at least ADOBE RGB and speak to them about making some test prints. Once you dial in your file prep and you get good tests, order the big print and then stick with that lab. (---You may be able to try soft proofing in your editing software)
The most important thing is how much effort you want to put into the process. There is no wrong answer, they are your prints and it is your money. Very nice prints can be made from JPEGS. Depending on the file, not all pictures necessarily need a wide gamut printer, others benefit a great deal.
It takes time and effort to find out.
The best place to start is by looking at great prints.
Like many things, getting to 80% of possible quality is easy, getting to 90% is much harder, above that Harder still.
Nowadays, 80% looks very good vs any historical comparison, but you will know when you see the really good ones.

I use Photomagico by Boinx. It’s not free but does everything you asked for. Photos and video clips can be dragged and dropped from Lightroom library view (if you’ve made them jpegs) Titles using any font on your computer are easy to do in any color and drop shadow or whatever. Any involved show with moves and audio and graphics takes takes many hours of work. From organizing and tuning up photos, to keeping things organized and then putting a show together is a huge job. I do one major show a year and I figure for every minute on screen is about ninety minutes of work.
Good luck. The first ten minutes of the show is the hardest until you get into the flow.
…Cam

We have the Microsoft 365 family plan. My wife, daughter, and twins use it more than I do.

I used Word, Excel, and PowerPoint for decades at work. I still use them occasionally, but they keep "rearranging the deck chairs," just to confuse me!

I could probably use Apple's Pages, Keynote, and Numbers on the Mac instead. Pages is reminiscent of the old Aldus/Adobe PageMaker, which I loved from version 1.00 in 1985 to 7.x sometime in the 1990s. It's even better and more intuitive. I never liked QuarkXPress or In Design. I didn't get their metaphors. I learned graphic arts in the days of Kodalith Ortho line film, rubylith, amberlith, and galley paste-ups. PageMaker followed that metaphor.

As a multi-image producer in the 1980s, I used 15 slide projectors, computerized dissolve units and controllers, a computer, a 4-track tape deck, and a lot of other gear to make corporate presentations.

TODAY, I can do the same sort of shows with 4K video produced on a MacBook Air in Final Cut Pro, a video editing software. You can also use DaVinci Resolve or Adobe Premiere Pro, or even iMovie or Adobe Premiere Pro Elements.

I use GarageBand on the Mac to edit audio. It has more tools than my old audio studio of the 1980s, and it comes free with every Mac.

As for copying old PRINTS, I use a home-brew replica of a professional copy stand, my MILC camera with a macro lens, and a couple of NEEWER LED panel lights I also use for video. I copy the prints to raw files and edit them in Lightroom Classic. For just a few at a time, I might use a scanner. But for dozens or hundreds, I set up the copy stand and batch originals by size.

To copy Black-and-White negatives, color negatives, and color slides, I use the process outlined in my white paper (PDF file attached below).

I'm extremely particular. I edit every image, to crop, adjust or restore color and tones, sharpen, remove blemishes and dust spots, etc. This can take hundreds of hours for a professional quality show. But the magic is worth it. I use Lightroom Classic and Photoshop to do that editing.

The use of video editing software allows plenty of flexibility. You can import both video and audio clips, along with still images. You can pan and zoom still or video images, with the Ken Burns effects. You can use hundreds of special effects, although I do so sparingly. You can add titles. You can import music from any digital source. Any sorts of things you might do for a simple motion picture can be done in video editing software.

Regarding music: Virtually ALL commercially available recorded music is copyrighted material. It is licensed for private, home use ONLY, unless you make other arrangements with the producer, composer, and performers, via a clearing house of some sort. If you use it without permission, in any sort of business or promotional context, you risk hefty fines and imprisonment. So proceed with caution.

If you upload to YouTube, music will be scanned automatically and your content may be rejected if you don't have the proper clearances.

I recently did a retrospective slide show for my Davidson College 45th Year Class Reunion, Class of 1977. I copied and restored dozens of classmates' snapshots, along with my own archives. We deliberately made the show silent to avoid the issue of the college getting sued for unauthorized use of music in alumni fund-raising (class reunions are MAJOR fund raising events). The show ran on big screens before, during, and after our class dinner. If you PM me, I'll send a link to a 1080P copy of that Davidson show. It's on a private channel on YouTube that I set up for my classmates who could not be at the reunion.

Plenty of "production music" is available for nominal licenses fees, if all you need is a simple music bed behind narration or images. I have used many libraries of such material. APM OmniMusic is my "go to" source: https://www.apmmusic.com/libraries/omnimusic-omn