Simple tags would fix all this overly complicated crap without getting into too many particulars: Bull-MC (MC sleeps with NPCs love interests - could be male, female or trans "bull" for functional purposes), Cuckolded-MC (love interest sleeps around on MC), Cheating-MC (MC cheats on love interest).
Anything beyond that starts to get even more silly. But something like this would be workable to give users a general guide towards what they're looking for, even if you changed the names of the tags slightly. Not that I think f95zone would go that route by this point, with all the tags that would need to be retconned.