Quinn reminds me of a girl I went out with briefly in high school. Huge bitch, bad crowd, I had a small group of friends that got into some shit with them but privately she could be really sweet. Found out one day - from the girl herself - that she blew one of the members of her bad group in the school bathroom to "see if their friendship was going anywhere". I'll never forget that exact phrasing. I broke it off and didn't go near her again. Quinn is kind of like that, but she's straight up with it, and I'm more mature now. I fully expect her to hook up with some other guy during the story, maybe to make MC jealous or as revenge or for some other fucked up reason, maybe as 'payment' for not reaching her sale quota in time. I'm braced for the blow (so to speak). Her backstory, her little expressions, her private affection with the MC, it's all gold. Quinn is DPC's deepest character right now, imo.
Heather is definitely for the DIK (and not for that bitch Tommy). Depending on how much attention she gets, Heather could even rival Lily as best new talent on the DIK squad. She's already okay with open relationships, she's clearly warmed up to MC (if you've played it right), and she's hot af. I'm on the Heather train baby.
I think the DIK girls (and I'm including the HOTs generally in this because Sage is DIK and staying with her opens up a lot of their interactions) are generally chill and non-judgmental. I like Jill's model but she drives me up the fucking wall, I couldn't hang with her IRL.