10 years ago building a 7.62x39 was tricky.
Not today. Good mags are the key, CPD/Duramags work best for me. Don’t confuse them with the older C Products mags, not the same. Newer CPDs have a nice slick Teflon like finish and strong springs for feeding steel case properly.
An enhanced firing pin is a must, and most BCGs come with them. If you’re running an enhanced pin you won’t need a stronger hammer spring, any GI single stage is fine.
I’ve had zero problems both with a 16” PSA upper and a Radical Firearms 10” upper.
The bolt is the weak link in a 7.62x39 AR so buying a good one or having a spare is a good idea. LMT is my preference but not cheap. Toolcraft is a fine budget option. AIM Surplus too.
The PS47 seems to be a good platform but the receivers are wider than a std. AR. With CPD mags and a 7.62x39 upper you can use anyone’s lower. The PS47 carrier is proprietary too.

If you’re like me and have a few AKs with Romanian, Hungarian, Polish & Yugo surplus mags, don’t expect them all to fit without mods. Running Magpul MOEs you’ll be fine.