In competition BBQ, you can turn in any part of the chicken you want to; they real key is ensuring enough pieces for all 6 judges (in CSBBQA and KCBS). Cooks use thighs more than anything else because as dark meat, they tend to hold moisture and texture better, and accept your flavour profiles better.....the smoke you apply, your rubs, etc. These are meat contests, and the judges need to still be able to taste THE MEAT when you are done doing what you do.
There is an appearance score, and thighs set up well best in the box, garnish or no garnish.
Teams can cook with skin on, or skin off. Skin on helps with the delicacy of getting that chicken entry just right; holds moister, etc. There is a pitfall in the judging area, however, because the judge should be able to bite through the skin and not have a big flap of rubbery skin come away from the entire entry.
Under the chicken skin is where the worst chicken fat lies. The last thing you want to give any judge is unnecessary, and unappealing fat. You have to dedice what you need in the cooking process and what is going to be unappetizingly superfluous at turn-in. At our last teaching course, one judge got an entry (chicken) with a fair bit of fat left under the skin, and that mark went down. I don't know if the cook that day did that deliberately or not, but it was a great teaching moment.
Crispy bits may not work in your favour if it seems the various parts of your entry are done to different standards. Be careful with this part. And an entry has to be cooked as a single unit on the fire; no separating, or taking pieces off and putting things back together later. At issue is your skill as a cook in achieving great barbecue that anyone would want to put in their mouth......and if you are good, barbecue they'd want MORE of!
Hope that helps some...........
"Barbecue is Murder! Tasty, Tasty murder......"
"PETA: People Eating Tasty Animals"