I know a lot of it probably is meaningless, but I remembered that in SBaHJ 2 they both 'do' one of them's mother and much later we learn Dave unknowingly finds his mother hot on like 3 different occasions so is there other stuff on SBaHJ that has meaning to the greater narrative?

The greater narrative meaning is that every Mom in Homestuck is Hot, and Dave easily falls down Freud’s Stairs at the slightest of chance.