The best engine protection for VAG engines is to be on the fixed interval regime and use the 502.00 0w-40 or 5w-40 oil so you're unwittingly killin' it (you're already doing this). Going high end on the oil filter will reduce engine wear more in terms of Castrol vs Mobil.
Castrol that you're using is a top tier oil but Mobil FS 5w-40/0w-40 is an option if you want to change brands.
Personally, when I've run the Shell Helix Ultra PurePlus 5w-40 in some VAG engined loan cars we have I've found the engine/valvetrain noise to increase after a few thousand miles. It's anecdotal I know but it doesn't happen with the Motul, Mannol or Fuchs that I've changed the Shell out for.