I assume from your post that the rear sits low because you carry around 200 pounds of gear. Take it out and the normal ride height should be restored.

All four of those sizes can be used at the plant depending on the weight of the vehicle based on engine, options, wheelbase, etc, so you'll have to inspect or remove them to see what your car has. Their purpose is to achieve the correct ride height for varying curb weight. Ride height must be maintained within a fairly narrow range to achieve desired ride and handling and meet bumper height requirements. Some manufacturers use different length or rate springs to achieve this. MBZ uses the different thickness spring isolators.

Contrary to popular belief, springs rarely "sag" or wear out from use or normal loads. They can be damaged from overloading and can "sag" due to loss of material from corrosion. The spring rate is a function of wire diameter to the fourth power, so it doesn't take too much loss of material from corrosion to cause them to lose rate.

As an example, if your car currently has 13mm isolators the 23mm versions will raise ride high 10mm or about 3/8", which is not much.

Years ago you could buy air bags that would fit inside the springs and they could be inflated to increase ride height or preload the suspension. They were popular with drag racers to counter the torque reaction on solid axle cars by preloading the suspension. In NASCAR/circle track racing it's called "weight jacking" or "wedge". Current GN/Busch cars and Craftsman trucks have adjustable height spring perches with a jackscrew that is easily accessible during a pit stop, so they can quickly change the wedge to improve handling.

Another bygone way to raise the rear was "overload" shocks, which were just shocks with a concentric springs to add to the rate of the OE spring. They were popular with station wagon owners who carried heavy loads.

Duke