1. nzxt h510 with all bequiet silent wings 3 fans airflow is pretty solid.
2. i usually have my window ac unit sent to 76 F.
3. it depends on the game for instance i play apex legends mostly and almost evertime i get a crash in that game my computer just restarts
3.5 i tried playing outer worlds for the first time since upgrading and it just crashed to the desktop when ever i tried to get into a game.
almost never an error, but i have gotten a couple crashes from apex that just crash the game and not my whole computer and those give me an engine error everytime that happens.