Definitely. The tone is set by the popularity and how much content the fandom can be producing, though there are closed canons still pushing strong too, of course, but a lot of times, they were big in the first place (like Harry Potter).

Possibly. From my experience, most fandom fights stem from a character or ship war and if there isn't much to be had of that, the drama tends to be less. Unless some fans are stirring up trouble for whatever reason (clique behavior or creating drama for drama's sake).

Unfortunately, a closed canon or an old canon doesn't mean that people still won't fight over it. They can't fight over what may or may not happen, but there is still things to argue about. You never can be quite sure what triggers people - new people in a fandom vs the previous fans is definitely not new so could be.