If a gay man were to try to have sex with a female succubus would this influence anything?
You would probably get an incubus or intergender incusucc lol as its a spirit that feeds on desire it will sense the gay man would want a male form anyway.
Ok lol what if I specifically asked for a female
That was my first thought too.
No it will not affect much. She will just Milk your balls irregardless. A relationship is a two way effort. Either you evoke her and have at the action or not. Although a powerful enough spirit can force you to have an experience if it so chooses and you are weaker than it. Imagine that, a sexy significant other throwing you on the Bed and pinning you down for a Wild Fun Time!