for the past few years I have been running my Octavia 4x4 AND an Audi A2 tdi on 15" Audi pepperpots like they use on the ROC Buggies and also BOBA motorsports crazy 1000BHP Golf.  

Mainly because they are 10lbs lighter than the 16/17s I was using previously and they also improved the ride quality due to increased sidewall (especially on the A2 which was 40 profile rubber bands with sport suspension)

 

Now that I am looking at purchasing a Superb II I am wondering what the wheel options are?  Not talking 19's or 20's but going the other way so 17's or 16's as the tyre options are usually a lot better and if there is a forged equivalent to the Pepperpots then the reduction in weight really helps improve economy as well as responsiveness..

16" wheels will clear the disks on everything except the V6 Superb. I'm running 16" OEM Octavia wheels for the winter, the ride is slightly more compliant (No noticeable change in cornering behaviour), but it's hard to feel much difference between 16" and 17". If big alloys and low profile tyres actually helped performance F1 cars wouldn't be doing exactly the opposite .

I can't help with specific alloys, but I do know the 16"steels with winter tyres are over 2kg lighter each than the 18" standard alloys with summer tyres. I am sure this is a small part of the additional ride comfort on the winters

having had 4x4 on the Octy I really noticed the change when I went for the lighter alloys with narrower section as well when I hit standing water on the motorway.  It just stays straight.