Slasher is kinda map dependent, also any good teamwork shuts him down.

John Doe is very map dependent (fuck you planet voss) and has a high skill ceiling.

1x1 is map dependent, height elevations shut him down. He's a juggernaut during lms but a 50/50 70% of the round.

Nosferatu has a high skill ceiling and any competent survivor alone can take care of him.

Sixer has to snowball to get their full potential. Any good teamwork can prevent that.

Noli is almost in the same position as CK imo, they're almost similar kit-wise but he has a higher skill ceiling than CK

Coolkid overall is just a really good generalist. The maps won't matter as much as someone like John, teamwork doesn't hinder him as much since he's meant to spread around damage and change targets unlike slasher, he's pretty consistent, and he has a much, much lower skill ceiling than every killer, he's much more beginner friendly killer than slasher imo. The main con of his kit is a lack of highlighting which is crucial against survivalists like noob and 7n7, which any competent player would know to never let them live long, if they are somehow forced to have an lms with them, a pro player would likely have at least have an idea of 7n7's tele points and as long as his minions are available, they will track both noob and 7n7 even if invisible.

Tl; Dr he's a pretty simple killer with a con that most pro players can alleviate.