I’ll just mention that the latest BIOS (v0807) for Asus Prime X370 PRO has added a lot of tweaking options in the form of the AMD CBS section, which contains P-State overclocking. Seeing this I wouldn’t be surprised to see this coming to more boards as well.
Unfortunately my testing has me conclude that P-State overclocking on this motherboard and for what I’ve read reported elsewhere a lot of others as well needs work. Primarily it doesn’t seem to be possible to directly control the voltage for a specific P-State. There has been whispers of another update from AMD to the AGESA code into the version of 126.96.36.199, and maybe it could contain improvements to P-State tweaking as well.
So it could become a great thing in the future.