The ZLE bushings do not add that much NVH, imo it's insignificant and a net positive. About the same effect as camber plates, but on the rear of the car. IMO, they make the feel of the car much better, you can literally feel the surface of the road through the tires and into your butt, you can feel what the tires are doing better. With camber plates you get the same feel through the steering wheel, and the two combined are a massive improvement for a sports car. If you just want it as smooth as possible maybe you should look into a Caddy instead, lol. Sorry not sorry.
IMO you're far better off with the GMPP ZLE bushing kit, it's not that difficult to install if you have the right tools, but whatever floats your boat is just fine.