Understanding plays

I'm almost a complete beginner of basketball especially understanding plays and who they're for, when to use them and who/when to shoot with.

I started looking at plays and trying to understand them. Several questions arose e.g. if I assign play type P&R Ball handler to Kyle Lowry (I use Raptors) and want to run play 15 Fade, who do I shoot with? The animation in assign plays shows that the center sets the pick and the pg goes around the pick and pass back to the center. But do I shoot with the pg or the center. The center clearly isnt ideal to shoot a 3 with.

Anyone care to explain plays for me? I understand its situational but there must be a general rule on what to do

In p&r, if your guard has space for shot, shot it, if your guard's space for drive, drive it to the paint... But if your center/pf has a passing lane and it'll open in paint, pass it 'cause it's more higher percentage shot and more easy basket for you...