In 2023 we did a trip to Switzerland and then a Rhine River cruise, end of September, early October. The first week we trained around Switzerland, Bernina Express, then Glacier Express, Zermatt, Wilderswill (a village adjacent to Interlaken on the way Lauterbrunnen, etc.), then Lucerne before hitting Basel and the boat. I had an A7Riv, 17-28 and 28-200 Tamrons, an A6700 and 18-135 was kind of my back-up just in case camera, also some video of trains. My wife and I both had cell phones with camera features.
In Switzerland, the 28-200 never came off the camera. Later, on the cruise side excursions, walking old towns with tight narrow streets, canals, medieval buildings, big cathedral exteriors and interiors and the like, the 17-28 got quite a bit of use. I didn't feel forced to swap at any point in Switzerland but that might vary with locations, or what grabbed my attention, etc. There's a lot to see and I was taking care to avoid missing things while looking through a viewfinder.
I can easily see using the whole 14mm to 200mm range. I would not want to have a 35mm to 70mm gap. If main carry was the 24-105, I might find it hard to decide camera 2 between 14-35 and 70-200. Probably 70-200 with a wide available?
There are funiculars, cable ways (like ski lifts, gondolas, etc.,) and mountain/cog railways all over. So one can be in town and then in the mountains pretty quickly, besides just walking with great views around the corners. etc.
Zermatt is a place where you will see all kids of camera gear. It might be hard to stand out as "that guy with all the camera stuff." OTOH, there's something to be said for considering how much you take and getting around with it.
We were off season and places were still pretty busy. Summer may be rather crowded.
