It would be nice to be able to brake and shift from the tops but it's not a position that you're supposed to spend a ton of time in, so I wouldn't say the design is backward. Most people I know with drop bars ride on the tops maybe 5 to 10% of the time. I almost never ride on the tops.

I would say that aside from the engine aerodynamics is the most important factor in speed. Weight makes a difference only if you're dealing with a lot of hills. So keep that in mind when you're looking for a "fast" bike. Something with wide flat bars positioned relatively high is going to slow you down some no matter what the frame is made of or how high end the wheels are. A bar that lets you get down lower with your hands no more than shoulder width apart will help, - even if it's a flat bar.

The final thing I will add is the for long recreational rides, the type of bike you use can make a lot of difference, but for short to moderate commutes with a lot of stops and starts, it won't matter as much in terms of how long it takes to get to work.