The cards contain data that designates the character as male or female. You can designate a female as futanari in the character creator and then there is a setting which will allow you to set a futa as the player character. Since the game only designates characters as male or female, it's possible for all the girls to be futa if you like. What isn't possible is for anyone other than the player character to be genuinely male. At best you can make an androgynous-ish futa and make believe it's a male.asking if card dropping any characters like on the girl regardless of gender being male x male or futa x futa works.
You can make male x male animations in studio by designating one of the males as having the female animation and some adjustments need to be made to line things up right, but that is the only way to make anything that is actually male x male. It can't happen in the game itself since the male or female data is encoded in the png file.
(edited awkwardly phrased sentence)