I mean personally I call myself a stan if I listen to their music, and I know the member's names and fandom name. But honestly, it depends on every person. Like, I wouldn't call myself an ikonic or inner circle because while I listen to their songs, I can't name every member. But someone who listens to ikon or winner may call themselves a fan if they can't name everyone, and that's fine too.
I only listen to title tracks, unless it's my ult group or I hear really good things about the b-side, or if I'm thinking about stanning a group or making them my ult group.