I'm keeping my vote on Mikey for now because I'm really not liking his responses in general as they dodge around addressing anything I brought up re: using flavor to solve. Instead, he seems very determined to tunnel me.
With that said, I'm willing to chalk his OG Theros god claim up to a joke in the context of the D1 godkilling jokes. On the off-chance it's not a joke though, my observation that non-Kaldheim characters are likely scum still stands.
I'd also like to note that I haven't played MTG since Avacyn entered rotation, so my knowledge of mechanics is rusty. Fortunately, there's wikis out there, and the official rotations list.
From a flavor solving angle, there's potentially more Planeswalkers to consider outside the Kaldheim set, but I figured that was less likely than using just the ones in the Kaldheim set considering there's only 13 players in the game. This also counts as another point towards Mikey's OG Theros god claim being an actual joke.