Adjusting a fuel pressure regulator

I am new regulators, just finished installing a Holley 12-879 to help lower and balance the pressure from the electric fuel pump.

To help knock down the pressure I have connected vacuum line to manifold vacuum.

My questions, when adjusting the regulator
1. Adjust when the engine is at operating temperature?
2. Adjust with the vacuum disconnected?

I am seeing mixed information when I search