There are so many settings on the cars that can alter the way they handle individual tracks it's nuts. So setup sheets would be the best way to learn what changes you make are doing.
All I know is from my old 90 Mustang that I did a lot of suspension stuff to... lots of caster, lots of camber...
I always start out with 0 preload on all my RC's and go from there. But I am not much of a touring car guy. And I am more just a basher. Not a racer.
There are a ton of things to learn about tuning your shocks, and I am definitely no expert. But I will say - tune a little at a time. On my...
Are they these?
If so... Part number 3988 is the set
Green springs #3941 12.0 lbs/in
Silver springs #3942 14.4 lbs/in
Blue springs #3943 17.0 lbs/in
Gold springs #3944 19.5 lbs/in
Red springs #3945 22.0 lbs/in
Copper springs #3946 25.0 lbs/in
Purple springs #3952 30.0 lbs/in
Yellow springs...
If you can't tell a difference in the spring rate, find something heavy enough to compress them a bit that will sit on top of one, and measure the spring. Do that with all of them and put them in order. Try the ones in the middle and see what the car does, and swap out to heavier or lighter...