Preload vs ride height

So I know that if you compress the spring on a coil over 1" you get 2" in lift, or close to. I am assuming this is for 600 pound coils. How much is the factory spring compressed to give the factory ride height?

Another question... if a certain spring force value is required to give a certain ride height why is anything other than preloading the factory spring a good idea? I mean, if you preload an even heavier spring,which ist seems all aftermarket springs are, you may preload less to ge tthe needed force but end up with the same force to hold the truck up and then every inch it collapses it will be even stiffer due to reater spring rate, so the ride would suffer. It seems to me you'd want a LIGHTER spring if you inteded to lift with preload so that once you got to the intended ride height it would not be so firm as it compresses if you want better ride quality. What am I missing here?

Example: Factory spring, 600 pounds (I know its not that heavy but this is for math) compressed to X weight for factory ride height. Compresses 4" before hitting the bump stops. That means an additional 2400 pounds and it hits the bumps.

Now if you used a 500 pound spring, then compressed it enough to give a 2" higher lift, it can compress another 6" and 500x6= 3000 pounds of force before it hits the bumps... you still get more offroad ablity than stock but get a softer ride than trying to preload the factory 600 pound spring.

Am I missing something here or is running heavier than factory springs in a coilover counterintuative?

Also, as the wheel drops away from the lifted ride hieght... it only loses 500 pounds per inch instead of 600 so it tosses bigger mud tires down into the ruts and dips faster.