"GT_DAY" is the default filter, it works well at all times, but I recommend switching to the other two when the sun is close to the horizon to add more atmosphere.
FPS impact should be minimal on decent high performance rigs.
To install, look for "assettocorsa\system\cfg\ppfilters" place the ini's inside for them to show up ingame or in the menu.
Hope people enjoy them as much as I do, cheers!
Gran Turismo Sport Inspired PPFilters v1.4
GT Styled PPFilters