All 7th Gen's are 5x100. You could've found the answer if you had searched. :faint:
I think the stock GT-S alloys were 38-39mm offset.
Offset depends on the width of the rims (as I found out in the past). I've got 18x8 with a 35mm offset. With that spec, a lower offset of 32 would sit real flush with the fenders, but rubbing may occur.
I think there's a member with bronze rims pushing 8.5" with a 32mm offset. It has a slight lowrider stance (i.e. wheels sticking out past the fender), but no rubbing.