Welcome back into the mtb fold!
I can't really answer all your questions but the way I ride is I try not to overthink my riding. Just do what comes naturally. Don't grip too hard. I usually position my butt behind my saddle when descending. Sometimes, no braking is the best way on some downhills. Don't hesitate, commit and just go for it.
Lots of YouTube resources on setting up suspension.
Enjoy your rides!