I was in a similar situation a little more than a year back. The Sony 24-105mm is my workhorse lens as well. At this point, I shoot with an A7III and A7RIII. I also have a Sony 70-300mm that I have learned to dislike.

Most would agree that the Sony 100-400mm GM and 200-600mm G are similar in image quality. There are pros and cons for each, and after careful consideration, I picked the 100-400mm lens. I am still very happy with that choice.

To me, the key factor was that the 100-400mm is considerably smaller and lighter, which makes it much more portable. For travel this is a serious advantage, and also if you have to carry the lens a lot. It easily fits into my backpack. Yes, it extends when zooming (in contrast to the 200-600mm), but that is a minor issue for me. It has a short focusing distance (just under one meter), so it has great macro capabilities. It also is a great landscape lens, and I like that it pairs with my 24-105mm without a gap. These two lenses are a powerful travel combo.

The obvious advantage of the 200-600mm is the extra reach, which is necessary for birding. I spend much of the year in Kenya, so wildlife shots are important to me. In most cases, 400mm gives me sufficient reach. I sometimes use Clear Image Zoom to extend the reach with good results. You also could add the 1.4x extender, which I am considering at this point.

I think that the key questions are how and for what purpose you are going to use your lens and if a focal range beyond 400mm is essential for you.

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There is so much bad information in this thread. Let me sum up some points.

1) Yes, you can put any E-mount lens on a Sony A7RV and take pictures. You also can put tires from the discount store on a Ferrari. Just don't expect good performance, from your Ferrari or your Sony. Inferior lenses will give inferior images, even on a 61 MP camera body.

2) Forget superzooms (anything with a magnification factor of more than 5x). Superzooms are convenient, but they make compromises that hurt image quality. They may not be so obvious on a 24 MP camera bud definitely on a 61 MP body.

3) Forget A-mount lenses. Sony gave up the A-mount years ago, and all A-mount lens designs are a decade old. None of them were built to handle a 61 MP sensor. Furthermore, you need an adapter to use A-mount lenses on a Sony mirrorless camera.

4) Forget crop-sensor lenses. Some suggested APS-C lenses like the 18-135mm. You can put them on an A7R5, but the results will be disappointing. Why use an A7RV in APS-C mode? Would you drive your Ferrari only up to third gear?

Read up what gwilliams6 writes in this thread. He is a pro with lots of experience with numerous Sony mirrorless bodies and lenses. His comments are always spot-on.

I think that this really good advice. This is a great lens that covers the basic focal ranges and that will be able to take advantage of the 61 MP of the Sony A7RV. I started out with this lens when I switched to Sony full frame, and it still is my workhorse lens.

I agree with the strategy, but not with the choice of lenses. The Sony 28-70mm is a very mediocre kit lens. The Sony 70-300mm lens is another mediocre lens. Unfortunately, I own it and really don't like it.

The best starter lens you can get is the Sony 24-70mm GM Mark II. It is pricey. I started out with the Sony 24-105mm, and it still is my workhorse lens. The Sony 20-70mm and the Sigma 24-70mm also would be good all-purpose starter lenses.

I travel with the Sony 24-105mm and the Sony 100-400mm GM lenses. The two really cover my needs.

As far as I know, there isn't a 28-300mm lens for the Sony E-mount. Sony makes a 24-240mm, but it is a mediocre. lens. Tamron makes an 28-200mm lens.

Having said that, you just bought perhaps the finest camera for photography in the market. Any zoom lens with a larger than 4x magnification will not do it justice. There are plenty of great lenses to pick from, but superzooms don't come to mind here.

PS: I agree that the B&H web site would be a great place to start your research. They sell pretty much any lens in the market. Their web site gives you all the specs. Once you identified lenses that might work for you search online for reviews.

I think that you should go by volume; don't go over 90 or 95 liters. Bags in that size category are usually between 26 and 29 inches tall, so it won't be over 30 inches. Getting a bag that is larger than what you need is not a great idea. You will have to deal with an oversize bag when you travel, and you will carry extra dead weight as larger bags are heavier.

I will second Osprey duffel bags. My partner travels with one and is happy with it. I personally travel with a very similar Eagle Creek Warrior model that is no longer made. I use it on my long distance trips between my home bases in Austin and Nairobi as well as to trips to Europe.

Here are some hints when you look for a model:
1) Don't go larger than 90 or 95 liters. A full bag of that size comes in right at 23 kg / 50 lbs, which is the weight limit in international travel. (Smaller airlines in Africa may have different limits).
2) The quality of the wheels is key. Stay away from the four-wheel models with turning wheels. They may be convenient on a smooth airport floor but not in the field. They also break much more easily. A quality bag has recessed wheels that are relatively large and have solid rubber "tires."
3) Stay away from cheap bags. They generally don't last. The bags we use are in the $300+ category.

Great--another great train ride. I took the ferry to Gudvangen and took the bus back to Flam. Enjoy your trip!
https://www.flickr.com/photos/zug55/albums/72157635189170998

That train ride is scenic, all eight hours of it. I stopped at Myrdal and took another scenic train to Flam where I stayed for a couple of days. I took a ferry ride on the fjord. You will enjoy this trip.

I have taken plenty of pictures out of trains and buses. I always get a high percentage of worthless shots, but I also have taken some great shots. Here is an album from a train ride from Oslo to Bergen, Norway, one of the most scenic trains I have been on. Most of them were taken out of a running train.
https://www.flickr.com/photos/zug55/albums/72157634904368192

Here are some hints.
(1) Sit on the shady side of the train if you can. If the sun is shining through the window it is hard to get a good shot.
(2) Get as close to the glass as you can. Make sure the window is clean at the spot where you plan to take pictures. Often you get reflections from within the train, particularly if the lights are on in the train. I often use my hands to keep the inside light from producing a reflection.
(3) Shorten the exposure speed as much as you can to reduce motion blur by jacking up the ISO settings and opening up aperture. In a high-speed train it may be hard to avoid motion blur. As others have pointed out, the windows may be tinted.
(4) Take wide angle shots. You will need to straighten and crop many images, so having extra room is helpful.

Also keep in mind that most train rides are not particularly scenic. It may be worthwhile to research to rail lines you plan to travel on to learn where the great photographic spots are. So I would not plan the entire train ride around getting one or two shots. Relax and enjoy your trip!

Sometimes answers are this simple. Now let's see how many pages of irrelevant information will be added to this thread.

I have traveled to Germany for work once a year for a quarter century for stays of one to three months--except for 2020 and 2021. Twice in recent years I stayed for six months. I have had the opportunity to photograph in many parts of Germany.

My standard equipment is a full-frame Sony 24-105mm. I complement that with a Zeiss Batis 18mm prime. I think that you will be fine with your full-frame 17-40mm and 24-105mm lenses. Sometimes I take my Zeiss Batis 135mm as well as that focal length allows me to see things differently and to be playful, particularly in large cities. But this is matter of personal preference. You likely will take 90% of your shots with your 24-105mm lens--the perfect focal length for travel.

PS: Why ship your clothes separately? If you ship your clothes they can get lost too. Most airlines allow you to check one bag (50 lbs.) to Germany for free. I never take more than one checked bag (wheeled duffel bag) and a backpack for camera, laptop, and valuables even if I am on the road for half a year. I have flown internationally a lot and never have lost a bag. At a few occasions bags were misdirected but showed up a day or two later.

It makes no sense doing a major upgrade and then get a full-frame DSLR. The Canon 5D IV is a fine camera but its technology is dated. Furthermore, there never will be another DSLR camera or lens. This is a dead-end strategy.

When I am not taking pictures, I am a scholar who has worked in many libraries around the world. So let me add a couple of points to the discussion.

Libraries are workplaces, not just for librarians but also for patrons. I often travel far to work in certain libraries, so the last thing I want is the disruption caused by photographers and their models.

The second point is privacy and confidentiality. I am entitled to reading any book in the library in complete anonymity. You taking a picture of me and the books I have at my workplace violates my rights. As a professor at a public institution, I am not interested in having pictures of me and the books I read circulating in the internet at a time of culture wars and book bannings.