I've probably put my Grand Prix through the ringer more in the past decade than anyone else on this forum and, at least for first gen cars, I feel the springs are the weakest link for how they handle. My car has the sportier FE3 suspension and the amount of body roll is still really high. I have a few pictures of it during track days while in a corner and while it doesn't look that bad I can say that you really do feel all the weight being thrown to the outside of the car. Braking is similar, you feel all the weight getting transferred to the front wheels during an aggressive stop and I've had the back end slide out from behind me a few times because of it. I think the best way to improve the handling for these cars is stiffer springs and better tires, but good luck finding a shop that will fabricate a new monoleaf for you. This isn't nearly as much of a problem with second gen Ws since those actually have some aftermarket options, but I do have a '98 Grand Prix and still feel like the springs need to be stiffer on those as well.
I will also add that I do think dropping the car by an inch or so will help so long as you have camber bolts or some other way to adjust the angle the wheels are sitting at, the center of gravity in these cars isn't that bad but it could be better. Macpherson struts aren't exactly the most adjustable setup, but the tires would really appreciate the weight coming down on them in corners at a better angle.