I smoked a 20lb spatchcocked bird for Thanksgiving at 250 for about 6 hours on mesquite a cherry and it turned out great. I would suggest spatchcocking them just due to cook time and also predictability of cook time. As opposed to say 30-40 minutes per pound, you're looking at 15-20 minutes per pound?
The bird I bought was in a saline solution, so I did not brine it. If you get one that is NOT in saline then by all means brine it.
I made a rub at the house with very little salt (remember I had a turkey packed in a saline solution), black pepper, white pepper, garlic powder, chili powder, cumin, and paprika.
I dried the turkey off with paper towels and put it back in the fridge about 4 hours before smoking. I wanted the skin dry.
I coated the skin with grape seed oil (any oil would work but this is what we use at the house), put on the rub, then put it on the smoker. I let the bird smoke for 2 hours then started basting it with a mixture of oil and rub every hour until it was done. Make sure you use a meat thermometer to gauge when it's done. 160 to 165 in the breast and the thighs will be done as well.
That turkey had tender meat, good crisp skin, and a good smoky flavor. There's a billion ways of smoking stuff but this is how I do it. Good luck and let us know how it goes!