I have an SC that was originally an lg4 so the springs are kinda soft and the ride height is really high, the rear spring code is NUX. I've heard the softer springs are much taller, if I put on IROC/WS6 springs, will it lower my car?

 

it all depends how many miles are on the springs. if your car was brand new, and the IROC springs were brand new, you would see about a half inch drop. But since your springs have some miles on them, they are more than likely sagging, if you replace your high mileage springs with lower mileage IROC springs you will probably see no change in ride heigth.
I had 143,xxx miles on my stock springs, replaced them with Eibach's 1" drop ProKit and my car stayed at just about the same heigth.

 

yeah most people do not notice much of a change when putting 1 inch lowering springs on a car which sagging bag springs...

the iroc/ws6 springs have stiffer rates to handle the extra weight on the v8 engine..