Once you've used adapters the offset combined with the wheel width will make the Q7 alloys unusable. AFAIK only the Q7 came with the 20" versions (though I would live to be proved incorrect)
Q7 will be ET60 and 9" wide, so there is room to fit adapters. 20x9 will be tough to get into the arches though, very limited in terms of fitting offsets.
I think the biggest 5x112 versions were 19x9 and there's a few 19x8.5 fitments.