I think you looped around on what makes the porn gay.

First two examples gayness is determined by the participants gender. In the third example gayness is determined by the sexuality of the participants.

If we have to observe both sexuality and gender of the participants, then I'd put forward that in futa the woman without a dick is lesbian to some extent. Thus driving up the gayness of futa. How much? IDK Let's put the penis wielding girl at half gayness, and the girl with the female genitals at 2/3 gayness, that brings the total to 58% gayness.

Frankly the only way to drive gayness down is to either not consider the sexualities or skew the men:women ratio.

Given the constraints put forth in the shitpost, only reverse gangbangs, in which the girls do nothing with each other, are less gay than straight one-on-one porn.

Or you could just go with the flow, and if it turns you on then make sure you're alone before proceeding.