reading this thread is making my head hurt
There's no way -2 camber the cause of "horrible ride quality." I have Aragosta coils with 14/10 rates (middle settings all around), full SPL arms, factory bushings, and 20 inch wheels, my ride quality is absolutely fine.
I've had other people, non Z people drive and ride in the car, zero complaints. Its firmer than stock but bumps and road imperfections are well managed. This is with street specs running much lower than a track car would, as its geared towards appearance . . . and its still fine
Refer to the factory specs here and the rear camber isn't even off by that much:
Stock alignment specs?
There is no way to adjust front anything without adjustable arms. There is minimal adjustment in the rear. For optimal alignment, you need all three rear arms and a competent alignment tech
I don't know how much reading you did, clearly not enough. I personally have posted endlessly that that anyone with coilovers MUST get adjustable arms, with the SPL ones most recommended because they never break, they're easy to adjust ON CAR, and they have manufacturer support.
What i do not see addressed in this thread are your tires. What tires are you running, what size, and what is the condition?