Not super so if you wanna mess around with GE-Proton and stuff. Personally I prefer ProtonUp-Qt though. It's a terrible name, but way less flashy, which it super doesn't need to be.
I've used both and found ProtonPlus to be better for my needs. It has way more proton and wine versions available. They also added the feature for steam games to select their proton version from the client as well.
Yea, for sure you can, but you have to go into each games settings one-by-one. In ProtonUp-Qt (seriously, terrible name lol) it's a list with a dropdown box next to each, the steam deck compatibility rating, and the ProtonDB rating that you can click to go straight to the page for it.