2 months late to reply to this but lol.
the main character was originally human but later in development the creator of the game had MC be whatever the player wants them to do be, faceless pretty much. so most fans just interest their own fursona with their fav romance option, especially for fanart.
So far I've gathered the MC is at least 6 feet tall since they mentioned Darius is shorter than them in Harold's route, and both Darius & Spencer are the same height being 5'11. Another route the MC mentioned they didn't have a tail either.