Superb HB 17 rims and wheel size?

Hello all,

Might be a stupid question, but I am having trouble getting help locally so thought someone here might be able to assist.

I am about to start looking for new summer tires and by tires Imean both tires and rims as I have put my winter tires on the 17” Stratos rims that my car came with.

The prices on the originals from the dealer is... not cheap. So I have been looking elsewhere and stumbled across these: 

Immediayely fell in love with them, probably because I could see them on mine (which looks like this one but without the rims).

However I am quite unsure about which size to get? Heard 20” is horrible for the ride, so thinking 19” maximum. But other than that?

Also looking at pairing them with a set of Dunlop Sport Maxx RT, but again no clue how to pick it so it matches and will actually fit on the car.

Any input is appreciated.