Welcome to our forum.
"My big question right now: Does this forum permit discussion of sex and organs explicitly or does it steer towards matters of relationship desires and emotions?"
For the most part, I have to leave that question for the moderators, and/or more experienced members; I really haven't been here long enough to give you a solid answer. What you're talking about might be permitted, maybe, but most of the threads I've seen so far tend to talk more about the emotional aspect of things.
It sounds like you have a good grounding in polyamorous matters, and I imagine you'll have valuable contributions to add. Any questions you have, we'll try to answer!