Welcome to the forum. Lots of good knowledge and suggestions here. I can’t speak for everybody, but I atleast haven’t seen anybody on here complain of driveline issues with the RL 2.0 sst under normal conditions and new upper control arm installed.
As far as auto 4wd, I think it’s still up in the air. Obviously RL suggests not using it. Off the top of my head I know moderator Jmzvet used auto 4wd in some snowy conditions awhile back and reported no issues. Others just choose to use 4 high or low in those conditions rather than relying on the truck to make that decision for them. In theory I can see the potential issue but I’m not sure how that translates to reality. Probably just depends on how much you actually plan to use 4 auto.