It partially determines breed. A chicken of a specific breed is that breed because of all its traits.
The reason you had such a hard time is because most websites are still stuck in the belief that Easter Eggers and Ameraucanas are the same thing, and thus, there's not much helpful references except on this forum to what EE's look like.
But, Easter Eggers are indeed not a true breed, and vary a lot. The most prolific characteristics of most are green legs, beard/muffs, and a comb that isn't single, V, or rose in type.