Awesome episode, and a theory --
Will/Jacob is bisexual while Billy/Paul is gay
Neither of the guys is straight. One thing that caught me immediately were the longing looks Will gave Billy when they first got to the house. It just seemed to be way too charged to just be two average straight dudes. And then in the preview for next episode it has Billy asking Will if Emma/Deborah knows "how much of a liar he is" - in other words, him pretending to be straight. Another clue about Will's bisexuality is when Emma asks him who his type is - he doesn't say "special girl" but stumbles as to what to say and then says something that wouldn't imply any form of sexuality one way or another.
Billy is really acting like a lover spurned because he hates seeing his "boyfriend" go off with the girl after all the time they've spent together. With that said, I personally think Will is more of a kinsey 2. He leans towards girls - he likes Emma more. While also knowing that Billy is gay and using that against him to make him do his bidding whatever that may be.
There have been theories that the Columbine shooters may have had something going on, unsure if that's true or not. But going all the way be to Leopold and Loeb - usually there are two killers who have a sexual attraction to each other. One is oftentimes bi while the other is flat out gay. Also this knowledge of actual feelings is used to guilt the other party and pull them further than they would have gone without them.
So far the show seems awesomely textbook and I'm pretty sure this relationship is funded upon the textbook notion of when two guys come along, hatch a plot to kill, and fall in love whether they knew they had feelings that way prior or not. Just when they got to the house it seemed very "text book" in their relationship together and how it worked - one guy pulling the strings of the other due to knowing actual feelings.
Will might also turn out to be asexual and is only sexual when seeking control and dominance, but right now I'm kind of doubting that because of his shocked reaction when Emma kills her mom. I'd think if he was that kind of sexuality, he would have seemed more turned on than surprised.
Basically they just seem like a modern day Leopold and Loeb.