Figure out exactly what kind of bike touring you're going to be doing first. If you're doing shorter trips you can get away with a very different setup than if you're doing a world tour.
Using a handlebar bag, frame pack, and giant saddlebag will allow you to travel much faster (less aerodynamic resistance) and use just about any drop bar bike. The disadvantage is that you can't carry quite as much stuff (which is also kinda good - less stuff is less weight which will make your ride a little easier to go distances). Something like this:
Lets you carry a change of clothes, bivvy sack, toothbrush, basic repair tools, spare tubes/pump, etc. That's really about all you need.
Nothing wrong with panniers . . . you can carry an awful lot more stuff. But it limits the frames that you can use, requires buying/fitting bike racks, it's much less aerodynamic (noticibly more effort to go distances/quickly), and encourages carrying more than you really need. If you can get away with less, it's worth considering doing so.
I say this as a guy who owns a touring bike, front and rear rack/panniers. :P I'd rather do a tour on a sturdy road bike than a touring bike these days.