Did you change anything else than voltage in BIOS for CPU power settings? When I was playing with power settings for my Ryzen 1700, the temps differed with same voltage for up to about 20-30 degrees.
Now I have 65-70°C in stresstest with R7 1700 @ 3.9 GHz with 1.375 V with AiO be quiet! Silent Loop 280
HWInfo shows the temps just fine, same values as RyzenMaster, so those temps are right.