Some of it is down to driving style. I find the far right setups have too much oversteer.

For the first one i did the same 2nd from right. But after racing Thomas' ghost he was so much faster than me on the twisties but i slowly gained on the straights. Had to be a setup difference and i thought i'd try all the setups. 2nd and 3rd form the left seem to be the fastest on all tracks
Wet setups seem to be a bug. Have no idea why they are faster

You can tell after a few laps which setups are fastest.