For destiny, I have no idea. I first played D2 when it launched and that was fine, but I attempted to pick it up again a year or two later and I was immediately lost.
For overwatch I agai haven't played in quite some time. But for multiplayer shooters like that I try to go into a casual mode or training mode first and just get a feel for everything. Eventually you get the hang of things.
For RPG's it depends. Some games can benefit from reading up online. For example I'm playing bloodborne right now and I had no idea how I wanted to spec out my character. So I looked up what weapons and abilities are in the game and made my decision based around that. If a game features a respec option, I'll be more likely to just go in and wing it and change things up when I need to.