Which extra camera would YOU choose?

Shooting with a second X-T5 will make RAW editing easier as you can sync development settings between the two cameras without issues. (White Balance and Exposure settings in particular can be especially problematic with mismatched sensors).

I mirror what everyone else is saying- my preference would be to keep it the same for control/menu familiarity. I would consider the opposite color of whichever X-T5 you have now. I did that and keep a telephoto on one and normal/wide on the other. Easy to grab what I need out of the bag by color.

Also, with the new app, changing and updating settings between cameras is a breeze. I can tweak and copy from one camera to the other via the phone app very easily. Although, I do really wish the icon/photo of the camera itself within the app reflected the actual color of the camera (the X-T5 is the black color only for both my silver and black body in the app). Also, not sure how (or if) backing up/transferring settings work between different models. Food for thought.

I use a pair of X-H1s for events and I thought I could use a small & light-weight camera for casual shots and as a backup. I bought the excellent X-E3 which I knew had a very different operating mode, but I thought that would not be a problem.

YMMV of course, but yesterday I went for a walk with the family and got them to stop for a few photos. It was so embarrassing as they waited impatiently for me to try to remember how to change the ISO value, how to set the timer etc..... and then all but one of the shots were OoF as I couldn't see where to focus point was set due to the fixed screen! So, any thought I had about taking the X-E3 on a shoot as a 3rd camera were killed stone dead as the action is often rapid & I can't afford to miss any shots.

On the other hand, the grey matter is not as quick as it was, so for me at least, any backup has to be identical with the main cameras.

Phil

One must be creative to do this as you are correct, one remote will not directly control multiple cameras. The solution is to create a chain where tripping one will trip the next. The photographer trips the first camera or uses a remote to trip it. The first remote camera has both a receiver and sender attached so that it can trip the next in the chair. This is how photos of rocket launches are accomplished. Just think about all the nice cameras, lenses and remote gear are sacrificed to get the amazing photos.