By spacing out the arm itself, the front track width changes, but the spring rate remains the same. Adjusting the front track width changes how the car turns in and off.
RF Out - Less weight transfer/Less Steering ("tire bite") going in.
RF In - More weight transfer/More Steering
Opposite on LF.
LF out - more overall corner steering/particularly center off and vice versa.
if you run a longer axle and change your tread width that way it will have more leverage over the spring and will react as if it is softer and there are times when i will run it that way just for that reason.Lengthens A arm/axle length making spring rate softer the bigger spacer you use.