Jake, I can't comment on moisture regarding jerky concerns, I do have the jerky dryer that works with the SI smokers as well as others. If it is a huge concern, just mix up up your jerky marinate and put the meat in a dehydrator. I've used dehydrators in the past mainly for jerky with excellent results. I've made a lot of dehydrator jerky! I will try my hand at jerky with the 3D soon, just having fun with different meats so far, don't let that deter your decision for a SI smoker though ;-)
Regarding the temp difference from the two butts vs the one butt in the photo, maybe 1-2 degrees warmer on the lower meats vs higher meat but I pulled them all at the same time. So far my smokes have all been good and moist even when smoking small amounts of meat or almost 40 pounds, it all came out very moist. I've also learned the importance of brining more than just turkey or chicken. I now brine all meats before smoking them, sure helps with retaining moisture and keeping the meat more moist than without brining!
Carl