What's the ideal tyre temperature?

Hi guys, I'm trying to get some setups done for the first time, and experimenting with different configurations, but there's something i don't really understand.

The only thing I notice when i change pressures is that i have more grip the lower i set them, but is there something i should know about it? I know about the tyre wear, but i don't really feel a loss of grip after it happens, so i end up setting the lower pressure available.

Also, i always thought the track would be more grippy the higher its temperature is, but i found out it's the exact opposite in iRacing.

Would you mind throwing some advice please? Some links to guides or something would be appreciated. Thank for your time guys!

Edit: if it helps, I'm trying to setup GT3 cars.