I am wondering if they ever fixed the bug with being a vampire and doing the companions quest. It'd automatically cure you of being a vamp at a certain stage of the companion quest. Not sure how badly if at all it'd break this mod

It does, but you can become a vampire again. I believe you can talk to Serena or Harkon about it.
Conversely, you can also become a werewolf again by talking to Aela.

It's not a bug, the two curses just don't play nice.

Before DG they patched the hybrid glitch, but now a new one has arose when you can be a VL, and have all the attributes but people don't see or call you one, and you can be a werewolf at the same time.