I swapped from 18 Rays to 19 Rays a few months ago and I also think the 19s feel more planted and certainly haven't ruined the ride at all. Having said that I never had any issues with my 18s.
Yes they bolt onto the hub then you bolt the wheel onto the spacer, had them fitted to mine for a few hundred miles but ive changed wheels now so I don't need them. google their website.
I use mine all year round with no problems at all. I think that ad mentions its a warm weather car and has never seen rain to push the point that the car is pristine. You see it on motorbike ads all the time.