I have done 2 nine pound butts, a 13 pound brisket and 6 racks of baby back ribs in one day but I always smoke all of them at 250*. Poultry on the other hand I do between 325* and 375*. I don't think having a full smoker makes much difference in cooking time. My brisket took 11 hours, my pork butts took about 9 hours and ribs took about 5 hours, which all fall into the time if I was just smoking them by themselves.
The last whole turkey I did was just under 13 pounds and at 350* took me 3 3/4 hours. For me I'm not crazy about the taste of turkey or chicken smoked, so I cook at the higher temperature. As for the drip pan, you can put it on the deflector plate or put the bird in the pan. If you put the birth in the pan, I would try and have it on something to raise it off the bottom so you don't get a soggy bird.
I usually rotate my meats all of the time so, if it looks like one is cooking faster than the other, rotate them. If it looks like the top is cooking fast and may get overcooked you could tent with foil. I always shoot for 180* in the thigh so you may need to tent at some point.
As for the baffle position, I have only moved it once when I used the grill grates and removed the deflector plate to reverse sear a tri-tip. For all other cooks I have my damper set between the 7th and 8th rungs that are close together on the side shelf. I don't count the most outer rung.
I actually went to a turkey grilling class today at the BBQ store I go to. I only went to taste turkey and get out of the house for a couple of hours. He did a 19 pound turkey using a ceramic turkey stand in a Big Green Egg. What I liked about the stand was that he mixed apple juice, chicken broth and a couple of table spoons of rub and put it inside the stand and then put it in a pan one the BGE. He grilled it at 375* and it took 2.25 hours. He took it up to 180* in the thigh and then it sat on the counter for 20 minutes before he started to cut it up. It was really moist. He also brined the bird 24 hours before he grilled it, which for me personally really helps in keeping it moist.
Good luck, hopefully someone has done ribs and turkey at the same time to help you our. As I said in a previous post, if you are in Facebook, join the Yoder Pellet owners group, there definitely be someone there that can help.