"I'm planning on getting some Ergon grips that will hopefully give me enough hand position options."

My Trek hybrid came with those types of bar end grips like the Ergon's. They are "cushier", but still your hands (which translate to neck angle, shoulder angle, hip angle-they're all connected) really have nowhere to go. I've never been to Atlanta or know anything about the riding conditions. I just hope that you don't get something and quickly outgrow it as your comfort & confidence on a bike grows.
If the flat bar works for you that's awesome. If, like me, you end up wanting more you can always buy another bike.

Keep looking until you find the right one. You mentioned one was obviously better on the bumpy street. Which one was that? Steel?