Selecting power valve method Holley 4160

This discussion is a fine argument for EFI! Seriously, I switched to EFI just because of how difficult it is to get all of the analog circuits in a carb dialed in correctly in a dual purpose car. The power circuit (PV) is a great example of how a fairly simple valve can become super complicated in practice. As Matt points out, the power valve opens and closes the circuit, but the flow of fuel is controlled by the pressure drop (which changes depending on loading) and the size of the restriction. 90% of hot rodders don't even know what a PVCR is. Walk around a race track and ask racers if they have ever adjusted the size of their PVCR and you'll get a lot of blank looks. (Same with IFR and booster channel size)
Fortunately carb engineers have figured out most of this stuff over the years and if you buy a good carb like a Holley XP, they'll be very close right out of the box. We run carbs on race engines all the time on the dyno and good carbs work great right out of the box.
As for the OP, just try some different stuff and see what happens. It is a great way to learn. If you want an educated guess place to start then copy what the Holley engineers used in a carb designed for your application. An even better guess is to copy what the OEM engineers did back in the dark ages when they used Holley carbs. You have to go back in time about 50 years, but Holley carbs were used on everything from tow trucks to muscle cars so there are lots and lots of examples of how real engineers came up with compromises for power, fuel economy and reliability.