Ok. When you want to find optimal pressure, with current tyre physics what you want is to have greenish- light blue tyres for optimal grip. tyre has 2 parts, core and outside layer. Added pic for you to have an idea, how tyres should look like with r3's on after few laps. So if you lets say, after 5 laps got blue/ dark blue color tyres- you got pressure too high. if tyre is all green, and outside gets close to red 115+ C, you need more pressure. I guess thats place to start.
Even if you give +1pont for rb4, it still wouldnt make sense to pick it, while without restrictions. It would be AT LEAST 0.5s slower per lap than xrt/fxo, a lot more on faster tracks. Bl1? 30 laps race, you would loose at least 15 seconds. That +1point wouldn't make RB4 competitive at all, couse picking it will loose you several places.
In NDR's winter event fxo had restriction of 3%, yet during practice fastest rb4 lap was around second slower than fxo's.
From my perspective, there shouldn't be any RB4's on grid.