I know this is a widespread issue among the Ryzen 3000 series, but here are my issues I have found so far:
Temperatures and core clocks in idle are very high in my opinion (52 degrees C) and 4,200 mhz. Because of this the fans go up and down in their rpm and it's very annoying in idle. Also the voltage is always 1.45V in idle, never dipping below 1.4V .
Also I have noticed my 3900X can't go higher than 4,200 mhz (where the advertised boost clock is 4,600 mhz) in a workload such as Cinebench R20 (my max score was 6912), PBO only, no manual overclocks.
AMD Ryzen 3900X
Noctua DH-15 with Kryonaut thermal compound
ASUS Crosshair VIII Hero Wi-Fi X570 Motherboard
Kingston HyperX 2x16GB 3600 mHz CL17 RAM
Samsung 970 Evo Plus 512gb SSD
Asus ROG Strix RTX 2080 GPU
Running on Windows 10 (1903) with latest updates, latest AMD X570 Chipset Drivers, latest Crosshair VIII BIOS update, everything up to date.
Also tried switching between all Ryzen power plans, and only used one monitoring tool at a time (Ryzen Master or CPU-Z)