I know from talking to several Lovecraft scholars, that CAS and Lovecraft influenced each other to a certain degree.

It's unfortunate that he's thought of as a follower of Lovecraft's in some places when they were pure and simple contemporaries. If anything, CAS was the better writer, at least by the standards of classical canon. Dialogue, for example.

He was no less fantastic than Lovecraft, that's for sure.

An evolution of Poe? No, I don't think so. The similarities are there, for sure, but I doubt there's much else.