How does the Fruma Mythic upgrading system work?

Hi, sorry in advance if this is a dumb question. I am wondering how the mythic upgrading system works, as I just got my hands on an Az Bow and was wondering if I should keep it, as if the upgrade systems let all mythics, or the ones they have modified to become decent viable, then I might want to keep it for my archer or sell it. Thanks.

 

I think they had a post on the discord explaining it, as well as a video. I'd recommend keeping it.