Carbon doesn't necessarily give a smoother ride, more depends on geometry, tyres, etc than just frame material. But it does dampen the buzz you get from irregularities in the road surface, and so can reduce fatigue on longer rides. This is why you'll see lots of steel or aluminium bike with carbon forks.

As far as the gearing is concerned, there's recently been a discussion of this in another thread. My own view is that once you are talking about needing a sprocket bigger than about 28 at the back, you'd be better off dropping the idea of a compact double chain set and getting a triple. Then you can have the range of gears you want while retaining closer ratios on your rear cassette.