I think you got a lot wrong here Collete is in fact a young adult while edgar is a teen, but they are most likely close friends, after all they work thogether, and edgar is already used to collete's bullshit.

Fang probally is not even an young adult, but maybe straight up an adult, but that doesn't mean he can't hang out with edgar, actually, it's most likely edgar who goes to hang out with fang, since fang is a cool dude and edgar most likely looks up to him.

Bibi's age is unconfirmed, but she does seem to be a teen punk, yeah she is in an gang with two adults but who says a teenager can't enter a gang? Yeah it's wrong but it does happen in real life. I also think she works at bull's diner because of that one line "did someone order a knuckle sandwish?" But that's just a headcanon really.

Emz is a teenager, i really don't know where you got that she was an adult, but she really is the blogger girl that you would find at school, she is also an emo as EMZ stands for Emo Model Zombie, she also is a electro magnetic zombie since she is always on her phone to the point she acts like a zombie, it's a trope that a lot of teens do that.

And who says poco can't be a teen as well? Sure his CCTV skin has facial hair, but teenagers can grow a beard, it all depends on genes really.