The smoke ring is a bit of a misnomer. As I understand it it's more of a chemical reaction that comes from nitric acid buildup in the outer layers of the meat formed when nitrogen dioxide from the wood smoke mixes with water in the meat. So, unless you have some wood chunks I doubt you will have much of a smoke ring in an electric smoker. Possibly, some from grease drippings.
As for your second question I can't answer that one.
Jambo J-3, Jambo Backyard, Backwoods Party, Backwoods Chubby, Custom Offset, WSM, and a Primo Oval XL.