That's probably as subjective as anything. I think readers select erotic fiction because they seek to experience the emotions they associate with something. If they pick a story that also has something else, it's probably because they think the desired emotions also have something to do with the something else. And it's completely possible for a reader to unexpectedly discover they resonate with something they weren't looking for.
I would keep my advice to an author vague and say things like "listen to your gut," "follow your first impulse before thought creeps in," and so on. If you feel like you're guessing too much about how or what to write, try to take yourself back to a point before you felt like you were guessing.