If you wana get more stable all core frecuency at lower voltage and lower heat, yes OC is the way to go (atleast thats what the tests Ive done with my Ryzen 5 3600 shows). In my Ryzen 5 3600 PBO and even PB tend to drop more voltage than whats necesary to reach a stable all core fecuency (I tested this with Cinebench and Prime 95).
If all you care is about single core frecuency, then don't OC, PB and PBO will get you there. As others worte already, PB and PBO do a fairly decent job, not great, but fairly decent.
And, once again from my exprience with my Ryzen 5 3600, if you wana get the highest frecuency from it, be it all core or single core (even if you have good airflow setup case), an aftermarket cooler is always welcome.