Correct way to find stable underclock & undervolt? (Ryzen 3000)

[Otto_iii]

So i have been playing with underclocking CPU because i noticed its decent way to mitigate overt gpu utilization/heat when i don't need it in some old games where fps is already exceedingly high (350+), and driver based frame caps or ingame caps aren't viable. however i am trying to figure out best way to check for stability.  

One test i have been doing is hot-runs at max all-core 1.325v at highest stable frequency in CB R20, let CPU saturate at about 70C+ then if i apply change to voltage and clockspeed as CPU is still a bit warm, if the voltage is too low the computer will immediately crash (black screen, restart.  No BSOD or anything, restarts a if completely normal restart)  However i wonder if this level of stability is not called for as i had seemingly stable (hard to tell) at much lower voltages while CPU Temps were kept cooler due to said lower voltage.

Difference of running 1.0-1.1V seemingly stable (no hot runs) and max temps staying below 48C and 55C respectively even after repeated runs, vs 1.2v seemingly the most stable where operating temps are roughly 60C (will not crash when swapping to it immediately after hot runs at 1.325v).  Currently i am trying to find ideal, perfectly stable but cool as possible undervolt for 3600mhz on a Zen 2 CPU. 

Any opinions or advice? Am i over-doing it as said undervolts will never see such high temps? Stability>all else though.