I'll start, I guess?
Generally speaking, "shounen"-centric fandoms usually leave a bad taste in my mouth and sometimes the fanbase is too biased towards male characters and/or care too much about ships, so it's...kinda wild to imagine that, lol.
I'd guess the most popular characters would be Takuto or Ayumu (since they have these vibes of being likeable for some reasons?? and get picked a lot in forum games) or so. Least popular would probably be Kiyo or Kazuki for certain reasons :3c
I don't want to delve much about ships since they're all underaged--but I guess I can expect a few or so. I can't imagine which are gonna be the most popular or least popular ones, though. I swear if I see any NSFW or anyone shipping characters that I obviously stated as siblings I'm gonna adfahgfda
Merchandises? Oh boy, I can always self-print if it's a keychain or badge but I'll sell kidneys for a nendoroid or scale figs. Or even plushes.
Drama...eh, I guess the "funniest" ones I can think of is if the antagonistic characters being mislabelled abusive for doing their "antagonistic" things. I don't know if I want or do not want to think of more, but it's funny to think of it, at least-