I live in IL so can’t comment on mountains, but I’ve put the cab (minus doors) through tight wooded trails with heavy contact and no scratches that jump out at me. I didn’t put doors on until December and just haven’t done much other than push snow since, but I assume they’ll hold up as well as other cab components.
The only rattling from the cab is on the flip windshield. Everything else clamps down solid, I used thread locker to keep everything tight. I am really happy with the doors.
For a real test I could drive it down some Illinois roads, probably accurately replicate some rough western trails...