This team profile covers the original New Mutants as they were early on – a sort of “Year One” era. It’s best to read this before the individual profiles.
Writeups.org is an encyclopaedia of characters in genre fiction — comic books, video games, action movies, etc. It offers illustrated, researched profiles. These also include technical data for role-players. If you need a robust understanding of a character’s abilities, personality, history, etc. this is *the* place to be.