I had the same problem of high voltage and high temp, what I did was to edit the power plan and set the maximum processor state and minimum performance state to 99%. Now the temps are under control mid 40s at idle and while playing games like FIFA and CSGO the temps dont cross 60. Whereas using handbrake max temps are 65.
Of course for the downside of setting max to 99%, the cpu is now clocked at 3.48Ghz and wont boost to 4.2Ghz but the temps are much better.
You can use this fix till you cant go for proper after market cooler. Probably Cooler Master Hyper 212 which is around 29$ or if you can go for a better one then Noctua NH-D15 is much better. I think so as the cooler with Ryzen 3600 is good when the clock is around 3.6 Ghz but with PBO enabled it clocks around 4.0Ghz so the cooler then becomes insufficient