With a lot of cars, you cannot at least change the gear ratios. Usually only the final. But on some cars, you can change the reverse gear ratio: ok, can be funny, but probably not very used
Also for steering locks (F/R)
For the Cortina you cannot change gear ratios, but you can do what you want with brakes (including handbrake)
Weight distribution cannot be adjusted
Packers like fast bump and fast rebound cannot be ajusted but the ride height can be set.
In a GT40, you cannot change gear ratios, except the final and reverse gear.
Weight distribution can be adjusted (F/R and L/R)
Fast bump, fast rebound and Packers cannot be ajusted, but all the other suspension sets can be changed.
In a BMW you can channot change the gear ratios, same for the radiator or weight distribution, but for suspensions, you can do more or less what you want. But no chance to change the caster or the ride height.
Maybe it's "normal", but it's difficult (at least for me ) to understand (as example) why you could change some part of the gearbox (final, reverse) and cannot change the other gears. Or why you can change all the suspension sets, but not the packers or ride height.
I agree that some adjustements would be very difficult to do in a race weekend. But, when you drive a race car for the second time on a specific track, you should have learned from your first race and should be well prepared and do not have the same "basics" when you arrive for pratice as the first race. So in fact, you would change thos sets, perhaps not during the weekend but before being on the highway in the direction of the race weekend