From my own research I've gathered
The GTS springs WOULD be an upgrade. They are coiled differently than Touareg and in theory are shorter, but since they are stiffer than Touareg springs you would likely only drop the car ~0.25 inch or so. You can count your coils/coil-diameter and then compare it to the Porsche Caynne GTS coils to get actual numbers.. its impossible to find spring-rates for either vehicle on the internet or by any parts department
In my opinion, the Hybrid springs should be an upgrade. The Hybrid is a heavier vehicle, has its own spring-set, therefore I'm going to inference that the Hybrid springs should be an upgrade.
H&R makes a drop spring set which supposedly enhances theory
The rubber spacers that offer 2" (and in Alex' case, 3" lift) should also in theory enhance handling because they induce more preload on the rear springs. This also should help reduce sag when towing