The Happy girl is not so happy as she is struggling to deal with the very real possibility her project will be a utter failure, as well as dealing with the fact she's considered a failure by her father and a joke by the denizens of hell.
The grumpy girl shows off a soft spot in her personality when around the happy girl and ultimately is trying to protect the happy girl. She also has a keen eye for warning the happy girl about getting involved with the hot topic guy.
Gay spider is best spider. However there are hints (more so in the comic and music video) that the gay spider that he's suppressing sexual and physical trauma with drugs and sex and is generally miserable with his (after) life, he also shows a somewhat softer side when he briefly shows guilt/regret when he insults the happy girls project.
Hot topic guy's entire presentation is hard to pin down. He clearly has a hidden agenda and only time will tell if he's truly just interested in seeing people fail at redemption or if he has more sinister plans.
Hot topic man is clearly a psychopath, while he is evidently a very charismatic individual that does not detract he is an incredibly dangerous individual.
These characters are not so one dimensional imo. Time will tell how they progres.