Are certained types of content like pregnancy, gay and incest clearly hinted and avoidable?
Yes. At least, definitely for gay and incest content, and I believe it's the case for pregnancy. I think the pregnancy only shows up in the ending, though, and I'm not sure if there's a clear way to say "I don't want any of the girls to be pregnant in the ending". The ending is just a series of individual pictures of characters with a blurb saying what happened to them at the end of the game, though, not a full-length finale story or anything like that.
Edit: Also, lesbian content is pretty hard to avoid if you play as a woman, but that probably goes without saying.