All these spring sets should be fine for racing. Assuming you have them for the right shocks, I'm guessing these may probably fit your generic 50-60mm shock. What height are you aiming for? I last had my tt02 set for carpet, when it came to car park bashing it was way too low as there's rocks all around.

What I see a lot on rctech is that people can ask for the best setup but there are so many factors, surface condition/type etc.

Have a look at thercracer.com

I think the m chassis run shorter springs? 4wd, touring car springs should be the same for the TT02 with your general wheelbase. A rally car is pretty much an on road car with raised ride height so it's fine.

Not sure on your last question. In terms of what works, you'll need to experiment. The joys of fine tuning.

I reread your initial question. If you flip the rear hubs this can lower the back. The fronts can be lowered too with the different arrangement at the arms - check the manual as it mentions it there.