So im planning a list of mods for my car including wheels, I have read and searched thru out a lot of threads around here trying to figure out the right setup for my wheels and tires but still couldn't reach a decision. I have a 2008 G35 Sedan and my plan is either to go with Concept One CS-5.0 or 19" Varrstoen TE reps. I want a setup that flush with the body or a bit aggressive at the rear wouldn't be a problem.

+ im planning on lowering the car on coilovers + BBK (most probably Akebonos)

Concept one offsets:

20x9x +25,+35
20x10.5x +25,+45

I got these offsets from Varrstoen:

Hub bore 73.1
19x9.5 +0 5x114.3 black
19x9.5 +12 5x114.3 black
19x9.5 +22 5x114.3 black
19x9.5 +30 5x114.3 black
19x10.5 +0 5x114.3 black
19x10.5 +12 5x114.3 black
19x10.5 +22 5x114.3 black
19x10.5 +30 5x114.3 black
19x9.5 +12 5x114.3 Full polished
19x10.5 +12 5x114.3 full polished

Lexus hub bore 60.1
19x8.5 +32 5x114.3 black
19x9.5 +35 5x114.3 black

My Questions:
1) should i consider different offsets between size 19 and 20
2) what would be a good setup for size 19 and 20
3) what tire size should i go with the wheel setup
4) any custom work should be done (spacers, negative camber, fender rolling, etc...)
5) what is G35 sedan Hub Bore size

and Thank you in advanced.