If you are only increasing rim size one inch, it will not significantly affect your ride quality very much, IMO. The larger wheel will probably weigh a little more, but you switching to regular tires will save weight over the heavy run flats. Run flats are known to ride a little more harshly due to their stiff sidewalls, so going up one rim size and switching to traditional tires may even out nicely. The larger wheels are mostly for looks.

I can't help you out with the spare tire issue. I was under the impression that if the car came with run flats, there was no spare.