Coilovers vs. Springs and aftermarket wheels.
 

How is the fitment, ie. size, width, offset, effected by coilovers vs springs, can I, say, run a 18x8.5+35 square with coilovers, but not springs. I have done some searching but have failed to find my answer. Please enlighten me.

People are currently running that on the car with springs.

It's not just about dropping the car cuz you want it to look good.
do some research, stiff suspensions will mess the handling up.
This car actually benefits from softer suspension.
Spring wise I believe RCE is the only company that is doing it right.
I don't care about coilovers so I know nothing.

I think I worded that question funny but what I am asking is,

Can I fit wider wheels and a lower offset with coils over just springs.

Doesn't matter either way.

Coilovers will give you more clearance, my 18x8.5 +44's were really close to the strut if i had coilovers there would have been more room. 18x8.5 +35 pushes the wheel further away from the strut so he should be fine.

Springs on coilovers are smaller in diameter than just springs that go on the stock struts, not to mention the huge spring perch on the strut itself. Thus you have more clearance on the inboard side. How much? Dunno...measure your spring diameter and when you look for coilovers, you should be able to find the size listed. Not sure what the standard is.