Thanks for the insights on how RPF fits in! That makes sense that there'd be different kinds of RPF and they'd match up well with some categories but maybe not fit others. I'm kind of fascinated at the idea of "RPF canon" and all the possibilities of it, I have to admit, and I like your examples of different kinds of canon materials. Sports RPF especially does sort of seem that wide open, doesn't it? It's this huge "world" of teams and "characters" and the possibilities are nearly-infinite and continue forward and backwards rather dauntingly through history...

You don't sound judgey of micro-fandoms at all! They're not everyone's cup of tea, but I think the appeal of them lies in that huge playful openness where really just about anything goes...