So I have R7 2700X on a x470 asus prime pro board, originally the voltage was on auto and all over the place so through bios I downvolted it to 1.3625V which is shown in HWMonitor but in Ryzen Master it fluctuates between 1.3-1.5
if you see 1.5v+ on your 2700x it's because the board has precision boost overdrive (PBO enabled)(out of spec TDP)
check HWiNFO during cinebench or PRIME if all cores get close to 4.2ghz then PBO is on
stock 2700x doesn't go past 3.9 / 4.0 under cinebech
been running my 2700x PBO since day one , sitting at 1.488v and 1.52v