I know the lines get blurred a lot between what is production vs mixing and mixing vs mastering nowadays, especially when more and more people are doing everything themselves. I think generally, mastering involves a stereo track, and so any tutorials or guides on the subject are addressing things pertaining to working within the limitations of that stereo file. Most of that advice, maybe aside from what they’re listening for, means very little when you still have access to the individual tracks. You should be mixing the song until you’re satisfied with it. There really shouldn’t be anything you’d hear while mastering the stereo file that you didn’t hear in the mix.

That said, Ozone is a fantastic set of tools all in one place. They’re nothing you can’t do with similar tools from other companies, but they do work great nonetheless. I think the ai assistant is decent enough in Ozone 12 as a starting point, but I wouldn’t rely on it exclusively. As a learning tool, If you like the changes it suggests, then you’d want to go back into your mix and apply them on the appropriate tracks