1) yes
2) it depends on the trail. For example, on a big jump you want it to rebound slower so that once you’ve landed off a big huck, the fork doesn’t fire the bike back at you. However if you are banging down a root ridden slope you want it fairly fast so it returns after every root, not just getting further and further into its travel as it fails to extend befor it hits the next root – known as “packing down”
If your course has both you want to set it either midway or at what you consider to be the best compromise.