I'm running 19" 8.5 ET45 with 255/45/19 and they sit perfectly level with the arches on the front, the rear you could possibly push another 10-20mm if you wanted them level, but they look perfect to me, pretty much how VW would design them.
Basing on that, you'd assume a 265, or 275 on a 9.5 with the same ET45 would look too wide for the van on the front, maybe not so on the rear.
I've seen that look before and it just looks odd to me, like you've got over sized incorrect wheels on the front.
That's not a criticism, i'm just wondering if they do 8.5 for the front and 9.5 for the rear both ET45, to give the staggered look, that might look less bulky and more factory.
I've gone down the incorrect wheel choice a couple of times, and it gets expensive and annoying after a while, so getting it right first time is a big bonus, because they won't take the wheels or tyres back if you get it wrong.
Or like Oli said, the ET40 instead of 45, might yield the same result as my combo.