Looking at a new set of wheels and need fitment gurus to help me determine how this setup will fit on a G37 Coupe.

Front: 19x9 +30 (+36 also available) with 255/35/19
Rear: 19x10.5 +42 (+20 also available) with 285/30/19

I'm lowered on H&R springs and will have a camber kit installed soon. I want to have the fattest/widest tires as possible while being as close to 0 camber as possible without rubbing issues. I also want the wheel/tire setup to be flush with the fenders. Would F:245 R:275 fit better?

 

I think the front should be fine w/ +30 & 255s
The rear will be a bit inside the fender, but you should be able to run 295s w/ 10.5" +42 on a coupe.
I'm running 295s on a 10" +45 on a sedan.
Here's a very nice coupe w/ 285s on a 10" +32 (and he's THE administrator, so he knows his stuff )
https://www.myg37.com/forums/3470852-post5.html
Here's another one w/ almost the same offsets as you mentioned and he's running 255/305 setup
(and it looks frickin awesome)
https://www.myg37.com/forums/3473373-post26.html
In fact just browse the whole thread for lots of ideas
https://www.myg37.com/forums/wheels-...fat-tires.html