I recommend adjusting tire pressure and running the synthetic benchmark to see which pressure gives you the shortest braking distance and highest lateral Gs. Typically you'll run the same pressure front and back, but not always. As a rule of thumb you can then subtract 3psi from that number as a starting point. Generally your tires will gain about 3psi when they warm up during the race. I do recommend taking test drives with tire telemetry displayed to confirm. A heavy right foot can really cook the drive wheels faster. You also will need to tweak the tire pressures depending on race distance. But I think -3psi from optimum benchmarks is a good starting point. Do rerun the benchmarks after making changes to tire compound, sizes, wheel weight, chassis (weight, bracing, etc), brakes.
Some cars come with adjustable aero stock. I recommend playing with that and benchmarking it as well. For really tight, twisty tracks, you're usually OK maxing the downforce. For tracks with long straights that will obviously kill your top speed.
If you have the racing brakes, it's worth benchmarking brake balance. Often a sublte tweak of a couple of percentage points is all that's needed.
Also, don't adjust everything. Tweak one setting, test, tweak, test again, then move on. You want to get a handle on what each tweak actually does. You can try test driving your car with a tuning parameter at each extreme to get a better understanding of how it affects your car.