225 - 250 will work as a smoker temperature. USDA recommends cooking ground beef to an internal temperature of 160 degrees. If you are using ground turkey you should go to 165 degrees. For a 3 to 4 lb meatloaf you are probably looking at about 3 hours but make sure you are cooking to temperature, not to time.
I have never wrapped it but I don't know why you couldn't. Just try to maintain the temperature as long as you can. Maybe a double layer of alumiinum foil, although some swear by plastic wrap; then a towel and put it in a clean and empty cooler.
Just want to make sure the temperature doesn't drop below 140 degrees for too long.
Let us know how it goes and don't forget the Qview
I've smoked a few and I smoked at 225-240 until it hit 160 and they were real good. I like putting bacon on top to add some moisture to the meat.
When I did a 2.5lb loaf it took 6 hours
I just did a 1.25lb and it took 2 hours.