My 28-400 is my new favorite lens. Only had it a week, but it focuses well and is sharp enough for anything I might print. With my D850 the 28-300 was my favorite lens.

You listed two options: 2X TC or cropping. Your pics don't really allow a direct comparison of that question. It would make a great thread if you wanted to put in the work, but I believe the work will show that the 2X TC has better detail than cropping.
The discussions about enhancements in Post is really moot because the question you ask is how to get the best image to start with.
The option that your naysayers choose is to buy a 1200 mm PF and lug the additional 6 pounds to the destination. It is obvious that better detail will be available with this solution. Is it worth the effort?
Remember that BETTER is the mortal enemy of GOOD ENOUGH.

I mount the camera on the tripod and stand in front of the camera. I adjust the direction so that the shadow of the lens is about equally spaced around the front of the camera, and voila the sun is in the middle of the frame. I also find that with the 600 mm lens and 1.4xTC I have better luck with the last few degrees moving the tripod feet rather than trying to adjust the head.

My previous experience was a D850 with the 80-400 lens. I never thought that was inconvenient or beastly at 55oz. I now have a Z 8 and the 180-600 lens. I am very impressed with the results, but at 75oz it feels beastly. I like the results with the 2x TC also, but that is more of a beast yet. I do bicep curls daily to try to convince myself that I am not 80 years old and these cameras are not beasts. I don't think it's working.

The ones I have tried stick at smallest aperature which is likely what you wanted anyway.

This is my excuse for a travel tripod. Weighs 1.25 oz, fits in any pocket and it has given me some good 1/4 sec exposures. It's just 6 feet of 1/8" nylon cord tied to a thumbscrew. Put figure 8 knots every few inches in the cord. Now you just twist the thumbscrew into the threaded socket, stand on the other end of the cord and pull the camera up tight and you have great two axis stabilization. No one has ever asked me not to use it even where tripods and monopods were prohibited.

JPEG

I do, but I also back up selectively to my laptop (photos, not the catalog). I can carry current stuff with me, and I can use Lightroom in the field, updating its catalog locally. when I return home FreeFileSync will update my photos to the desktop and Lightroom will add them to its catalog. Seems to be a minimum work solution for me.

I use free file sync (freefilesync.org) on my pc. I have been very happy with the results, and they claim versions for Mac OS and Linux as well which I have not tried. You just need to tell it where the pictures and the catalog are and where you want them to go and it makes a copy then it updates the changes whenever you ask. It has a feature that lets it run in real time copying changes as they occur if you want.

I have to go with 10.

I have been using a Z 8 and the 24-200 f4/6.3. This combination is 28 ounces lighter than the 70-200, has a wider range and I find I don't miss pictures due to the smaller aperture.

Thanks. I had been putting that one off since it seems to be the hardest to understand. I will check the results.

I used AF-C Single point mode. The lens was the 24-200/f4-6.3 at 200 mm. I did not try to compare other modes with this subject. What I was prompted to do was to use all the modes and try to find subjects that photograph well with those modes. The point, if there is one at all, is that I got results that amazed me with the first effort at "practice". I very much respect the capability of the autofocus.

Thom Hogan, in his Z 8 guide recommended lots of practice with focus modes and all the focus controls on the camera. I might have gotten the same result without his prodding, but this shot seems to make the effort worthwhile. This is a crop from the center of a 200 mm shot hand held at about 10 feet.

It seems like the problem is obvious - the web where I care about it is the same color as the sky behind it. I could imagine a dark backdrop, but I like the background as it is. Does anyone have thoughts about using a flash or other technique to emphasize the web? How should the web be made to show up in front of the sky.

Details: Nikon Z 8 with Nikkor Z 24-200/4-6.3 set at 64mm, f10, 1/160 sec. ISO was auto and the camera picked 140. This is about an 80% crop from the original - just to get the file size down.
Location: South Coast Botanic Garden, Palos Verdes Peninsula, CA near the rose garden.