[FarQ]

those would be perfect as they should be from a RS5. it will move a bit closer to your wheel arch, but there should be no rubbing

 

[FarQ]

What do you think about tire choice, looking at the 265 or the 275

i would go 275/30R20 as it will give you more options and is a fair bit cheaper than 265/30R20 (at least in Oz!) Pics of mine below: