When setting up for max grip, we generally tell the new guys to take a piece of chaulk and mark 4 lines around the perimeter of the tire, from the sidewall to the tread patch. After a lap or two, look at the chaulk, and you’ll see exactly how far out that you’re pushing your grip. Obviously you want all the patch and none of the sidewall for max grip. Starting a bit below the “max pressure” on the sidewall and working your way down is a good way to start.
The heat affects r-compound tires WAY more than street tires, so keep that in mind. Once you get an approximate pressure dialed in, you’ll play with them on the day of to suit the conditions.
As far as drift pressures are concerned, I’ve only ever played around on an autoslalom course, so I have no idea…lol