Yeah he's a fairly well known extreme overclocker and he's partially responsible for Asus's implementation of performance enhancer lvl 3 and 4 so he's gotten a good look at the bios. Asus also includes his memory timing presets in the C7H bios.
PBO logic is basically all taken care of by the CPU itself and it uses the CPU's onboard voltage and temp sensors so it doesn't really matter what the BIOS or Ryzen Master do since all they do is report max power/current limits to the CPU with PBO on. Even if you change LLC levels the CPU will just change the VID to compensate and get the same voltage at the CPU SVI2 TFN sensor. If you add a voltage offset to overvolt or undervolt the CPU will just drop the VID until the voltage at the cpu is safe(when overvolting) or raise the VID up to a max of 1.55v until the cpu is stable(when undervolting). Even the SVI2 TFN sensor doesn't tell you the whole story because within a die Zen can feed
different voltages to each of the cores. AMD knows how their silicon behaves better than us so I wouldn't worry about precision boost overvolting. The cpu can even change voltages/frequencies 2000x faster than hwinfo's default checking interval and 100x faster than the fastest checking interval allowed.
I also saw better performance for all core loads with manual overclocking on my 2950x @ 4.2GHz, but my temperatures were going above 75C over extended loads. The problem is that on 12nm it's not just voltages you have to worry about. People have seen degredation at 1.38v @ 60C and PBO itself will throttle back voltage bit by bit for every degree over 70C so temperature is just as important as voltage on 12nm. I'm extremely wary about setting a manual OC unless using well under 1.375v to give myself some headroom because 1.375v@70C is right on the edge of what ambient cooling can sustain so all it takes is some higher than average ambient temperatures to make your OC unsustainable at max load.