I'm striving towards nothing being mandatory! Sex is somehow completely optional in my porn game
. I have it set so that you control exactly which kinds of NPCs show up in a sexual context. If you don't want to sex any masculine NPCs but don't mind girls with dicks, you can set it so that feminine NPCs with dicks is fine. Or if you don't ever want dicks or masculine NPCs, you can set that too.
Works with femininity and vaginas as well, can make the game strictly M/M or F/F. The only thing that determines the orientation of any of the scenes is the identity of your PC. Go wild! Most of the unnamed NPC events have variants for almost everything, but the more fleshed out NPCs' gender and biology can't be changed. NPCs are never choosy with the PC though!