Betazoids would be interesting choice. Look just like humans other than the black eyes. But their telepathic abilities would make for some interesting interaction.
Idk about Vulcans. No emotion, seems like that would lead to very boring sex. Then again, Spock's mother is human, so it was supposedly enjoyable enough.
Better off going with romulan. Exactly like Vulcan, but they have emotions.
Sex with klingons is usually not recommended, many times in star trek episodes. They are much stronger than humans, and could potentially cause some serious injury. I'm pretty sure I wouldn't be able to control a Klingon woman, and I'd be the one getting raped, lol. That and the head plate things dont do anything for me, altho maybe a half klingon, half human, their heads arent as extreme.
And of course, can't forget the classic Orion girls. The green skin is exotic.