BTW, "heart" does not mean romance (have you guys checked out About Death, which they gave as an example of the Heart category?). Think of it like this. What kind of a reaction do you hope to see from the readers?
"MIND = BLOWN!!!!!" <--- Brain comic.
"MY HEART HAS MELTED and/or BROKEN" <--- Heart comic.
Brain comics tend to be very clever; either the structure is clever (e.g. this was actually an amateur comic I read on Naver, and it was a vertical scroll comic that formed one story while reading down -- then you read it back up and it forms a different, but still coherent, story), or you have a highly intelligent cast trying to outsmart their opposition (e.g. Escape Room, Death Note).
Heart comics can certainly have romance, but are in no way required to!