Not really an issue. If you get a front puncture, jack a back wheel and replace it with the spacesaver, then replace the flat front with the full size good wheel. It's a bit more faffing around but probably adds no more than 5-10 mins to the wheel change👍
We use Shell V-Power E5. It contains fewer additives than E10 and has a slightly higher octane rating. Used lots of different fuels over the years in two RS5’s, a TT and a couple of A6’s, and , to us, this one seems really good.
Stick with E5 and you should be good.