From what I have seen in the trial, I think MG believed in Chad's teaching, without the killing part. But I'm not convinced DW ever bought into ANY of the main ideas that Chad invented.
The relationship of DW to CD, by all accounts, is that DW is a fellow "teacher" with his own set of beliefs (ie, not a subordinate in any way), and DW preceded CD. They ran in the same "get prepared" circles (if I understand correctly), but Chad's light/dark and zombies and "we are the gatherers of the 144,000" and the ideas of CD/LVD personally interacting with Jesus and Moroni and angels, all that was invented by Chad (and/or Lori). That being the case, I would expect other "get prepared" teachers might tend to look at such ideas side-eyed and with significant skepticism, and perhaps with some degree of superiority to CD, and the fact that DW did NOT co-publish with CD hints that he might have been one who all along felt it to be a lot of hogwash. As I see it.
I will add that I think that DW was in their orbit at times because CD and the others were still hoping to persuade DW to buy into the nonsense, and using various means of attempted persuasion (including sleepovers, marriage, private talks, etc) but to no avail.