think of it this way:

1. the shock oil handles/absorbs the landing, NOT the springs. compression of the springs does not absorb much energy compared to the oil in the shock. actually it's the air bubbles in the oil which are compressed.

2. the springs do the opposite, open the shock back up (out). so if you have 2 sets of shocks (lets say heavy in the front and light in the back), the heavy set in the front will open with more force than the backs. if you are in mid air, that will cause the the nose to point down as there is more force pushing downward on the front axle compared to the back axle.

3. if a shock is preloaded, it doesnt need to be compressed before it begins to push back out, so it rebounds sooner.

that's basically how a shock works on r/c cars, once you master that, it's pretty easy to figure out how your car will handle.