this is a tuff question, all i can do is go off whats on mine which is the 18 by 9.5 with 30offset all round
Ive just measured mine and ive got 323mm at the rear and 329mm at front, that the distance from center to the arch.. so mines bout 15mm lower and i have very firm tein coilovers
Id really recommend rolling your arches , its bout $50 an arch and then theres less hit and miss with all the options you've gave, atleast on the front because when you try and get up driveways and odd angled entrances etc, on a steering lock your wheel arch might dig into the tyres.
On the front , 40 offset is safe, 30 offset should be fine, and 25 offset borderline, should all clear the strut ( assuming you dont have rolled arch and the suspension a bit soft and a tight steering lock going up a driveway) if you roll the arches , all are fine
On the back, 30 offset you'll have to stick with 245, might get away with no rolling wont hit strut
38 and 40 offsets you'd go 255 , with rolling 265? shouldnt hit strut
Hope that helps a little, on my car the rim is about inline with the arches so i think its about the limit of offset, but others might say otherwise.
feel free to correct me if im wrong anyone...