As an old fan of the original Choose Your Own Adventure books (which were not sexy and were written for children), my tendency is to follow their lead and write in second person. YOU are the protagonist, YOU make the choices, YOU watch her tits bounce wildly as she rides you, etc. Not everyone is a fan of either writing or reading that way; one of the biggest issues is that when you read such stories, there will be times when the protagonist does something that you yourself just wouldn't do, and it totally spoils the suspension of disbelief. On the other hand, it makes the story extremely immersive. I think that as long as one writes the protagonist as a character who represents what most people would actually like to be, it works; it's the one time when you can create a total Mary Sue and still have it be something people actually want to read. And, it's important to anticipate where the reader would really want for there to be a choice, even if you don't actually plan on writing more than one branch there yourself. For instance, when you get to a part where the protagonist is about to have sex with someone, it's vital that there be a choice there insofar as whether they go ahead with it or not, because that's a choice people will want to make themselves.
I feel I can write from the either a male or female POV, but if she's female she's going to be lesbian. That's just my personal preference; I would rather not imagine and write from the POV of a character getting turned on by and having sex with a man, because I myself am sexually attracted only to women. I'm writing here for fun, not money or accolades, so I write how I wanna.
