X-T3 used buying guide and other questions

[verstovsky]

I wanna buy X-T3, but only can afford used one. What should I check first, and what any other possible weak points of camera in term of use etc, which I should be aware of?

I'm interesting also in evf behavior in low light (my previous experience with 2.36 evf in other camera in low light was a bit painful, a lot of digital noise so I barely was able to (manually) focus), and since I like to shoot in low light, what's the possible slowest shutter speed I can get without blur handheld with 50mm f/2 wr lens, for example? And generally, how good non ois wr lens and is lack of ois/ibis in low light is actually that important? I also heard couple doubtful messages about 50mm f/2 being "not that sharp".

Also, how much if any weather sealing gonna be affected after repair, after shutter replacement for example (and in any other cameras, not only Fuji)?

And the last question is, is there any simple and fast method to crop to 4:3 ratio in photo (I just prefer 4:3)? Like in camera menus or something, or at least to put on some framing grid etc (it's really simple in any post, but I wanna see my 4:3 during the actual photo shooting if it's possible)?

Afaik some other cameras have 4:3 mode, and I didn't find that Fuji have one and I hope it'll be someday implemented with firmware update.

Thanks for answers.