As far as I know negative voltage offsets are not advisable on a zen2 cpu because the bios will just increase LLC to tackle that. For this reason youtubers like optimumtech thought for a brief moment they could run zen2 cpus at insane undervolts with an all-core overclock. He had to correct himself later. AMD specifies that the high voltages we see only apply for brief periods and only in low wattage situations to stabilize the cores with as low ampere as possible to allow for low powerdraw. I am on my mobile and dont recall the source-post for this.
I can do some negative offset on my rig, not much, about 0.02v but even that keeps voltage down to less than 1.4v at idle where it's known to get too high when absolutely not necessary. BIOS with latest AGESA 1003ABBA keeps voltages in check better.