I daily drive my Z and I've got the 12" resonators and CF mufflers with stock cats. It's fairly loud and beefy. I do notice a fair amount of drone at 2.5 - 3k RPMs at highway speeds. Cruising at 40 and lower, the exhaust is very tame and comes to life on acceleration. Initial cold start up it's loud and has tripped some of the alarms in the garage at work lol after maybe a minute, it settles down and then you don't even notice it.
It doesn't bother me but typically it's hard to keep up a conversation with people that are soft spoken lol The Z's cabin is already pretty noisy because of the tires and road noise, so the exhaust could make it bad for you if that stuff bothers you already.
I added some second skin sound deadening in the hatch area and it's helped block out the annoying road noise and still keep the nice exhaust note.
Here are a couple vids I made after installation: