What is max voltage memory will Z590M Phantom Gami

I'm guessing a bit, but looking at the memory qvl, I some modules there that require 1.5v, so it seems it will go over 1.2v.

I also found a review of the next tier up, the 590 itx/tb4 on techpowerup and that states it will go up all the way to 1.8 in 0.01v steps. I'm not sure the one you mentioned will have the same range, but in general asrock's bioses tend to be roughly the same across the range, so probably also on this option.