i noticed fast guy put almost full pressure on tyres while default race set up has quite less

whats best and why?

I don't suppose logical thinking has ever been your strong suit, has it?

Read the setup guides here.

Maybe he was using R1? They are quite easy to heat up, hence the high pressures to avoid overheating. (Default set uses R2)

there is no thing like "the best setting", read some setup guides and experiment.

Generally it is better to choose the softer tire compound possible, and then try to keep it in normal temperatures.

I use R1's (1.55 bar) and i can go for 6 or 7 laps (keyboard driving) around BL but if i put like 1.10 or something if the same setup and i can only go like 4 or 5 laps in BL so i guess that they use like that to race longer if the tyres in "green" temp. or for bigger races.

fbm= r1 for lap count u want ... my pressure is 180/160 + wings 6/5