Well, it's hard to compare Kevin to the other characters since he's so recent. He was introduced in September 2010 in the Veronica comic series In his initial storyline, "Isn't It Bromantic?", Veronica expresses interest in dating Kevin but he is uninterested. As he and Jughead bond over their mutual love of food, Kevin explains that he does not want to date Veronica because he is gay. Kevin also bonds with Veronica and they become best friends.
I wonder when Reggie will play a bigger part of the show. I'm surprised (but happy!) that Kevin is part of the "main group" but not him.
Btw, how big of a character is Kevin in the comics?
He has had like 3 different solo miniseries since then and appeared in other stories as a character the same way a Reggie or a Cheryl do. So not a main core 4 level character, but probably mid tier above Moose or Dilton, who rarely get their own comics or stories.