Have converted two road bikes to flat bar. They ride just as fast and with basically the same characteristics as they did as drop bar bikes. The two main secrets is to use the correct bar ends to get the flat bar road shifters.
My problem with drop bars is my hands go numb on long rides being parallel to the frame. Love my drop bar bike but after two hours my hands go numb even with extra padding. Same road bike after flat bar conversion I can go more than four hours. So have come up with the following solution.
ONZA long bar ends placed as low as possible on the flat bar can give a position just a little bit lower than ridding the hoods. Have them so your wrist just about touches the flat bar when going over it. This gives you a second wide grip that is more aero and not parallel to the bike frame like drop bars. Have tried the Origin 8 long bar ends. The angle just dose not suit me at all. Lizard skin bar end covers seem to work well for this. Again you want long "L" shaped bar ends pointed down not up. This mimics handle bar used in europe and not readily available here. Alt bars are fun.
Shimano and Microshift both make thumb shifters for road derailleurs. The Shimano ones even have half clicks for the front derailleur. Not sure about the Micorshift ones. This gives you the same road gear ratios and derailleurs as the drop bar crowed. The Hybrid bikes seem to have different gearing than road bikes.
In short I have a TREK FX and it is not at all like a road bike, If you want a flat bar road bike put a flat bar or Alt bar on a road bike. If you want a touring bike or a Hybrid bike get that kind of bike. They are mostly not as fast as a road bike but have their own advantages.