I had reported in a few threads about some weirdness with Ryzen in Win10. Not performance per se, but things like not downclocking when idle even when UEFI was set right, weird all-cores-frequency-lockstep stuff, high CPU voltages, that kind of stuff. It was ALL due to AMD's Ryzen Balanced Power Plan. Somewhere in the Ryzen+ coverage or comments, it was mentioned that AMD was now recommending with X470 to use Windows' Balanced power plan. I usually use Windows inbox drivers for most stuff other than GPU, Samsung NVMe, and sometimes Intel NIC, but I didn't realize the "damage" that could be done by a non-inbox power plan. And to be honest, I probably haven't looked at the Windows power control panel in months, and this isn't exposed in Settings. I switched off AMD's plan and then deleted it. Everything mentioned above is normal now.
I knew something was weird for months, but yesterday I had HWMonitor open along with Task Manager, and an idle desktop. CPU voltage through the socket on my Asus ROG Strix X370-F was showing 1.45V AT IDLE! 0% CPU util. During system loads Vcore was going down to 1.25 and 1.32! It was like high-level LLC on a CPU running at Auto, as in non-overclocked. I know Asus isn't that far off after 14 UEFI updates, and then I remembered the power plan thing. With Windows Balanced, once again, everything is normal now. While typing this, Vcore is 0.937, and CPU is 1400-1550 MHz. Normal!