OK, wow, THAT is super helpful. I will study this more based on your comments. For my application I may actually want a stepper motor, so I will think more about what I am specifically trying to do.
Regarding the cap, it wasn't obvious to me that there was one on the Adafruit shield, I looked but I was expecting to see a 'large' barrel type on the board and I didn't see one. I should have checked the Adafruit circuit diagram.
I will eventually report what I do and the results I find.