How a bike fits you is such and individual thing, and what one guy finds comfortable another may not. Best thing to do is try and pull a demo ride from that dealer.
As far as power goes, it's enough to keep up with most bikes as long as the speeds are sane. It'll do 115-120 mph if you push the bike to it's limits and that's more than enough for most people. A stock 1200 puts out around 68hp, so the numbers are close, but the Harley has more torque, and they need it since they weigh about 50 lbs more than our bikes.
It's only when you get to riding 2 up with luggage on a trip going up mountain grades and into headwinds that our bikes show their lack of performance. since you're a solo rider, and you should be until you get some experience in the saddle, the America is a good first bike for you, and for many of us it's all the bike we'll ever need.
