Do not use the pressure relief to adjust or set your pressure. It's an upper limit, consider it a bypass. If you are constantly on the bypass, you are forcing too much oil into the bearing clearances.

The only engines that should be using 20w50 are worn out engines that need oil pressure because you do not feel like fixing it properly, like a rebuild.

Same with High Volume oil pumps. They were made for installing on a worn out engine.

Anything with clearances within spec will need a standard oil pump, 10w30 and you will have enough oil pressure for any conditions. I do totally agree with DaveJ's comment on horsepower. We build these engines with performance in mind. So why send more power to the oil pump drive than you have too?