Trimming: Some trim close. I leave a nice 1/4" fat cap because frankly I'm too lazy to trim it close. Like I said below though, I'm not competing, I'm eating. The guys on TV trim it close so that's probably what works for competition.
Wood: Personally, in my WSM I never use chips. I prefer chunks buried in the charcoal and throw more on about every 90 minutes to two hours if the chunks are small, like golf ball or raquetball size. Your mix of woods is an interesting choice. I have used cherry or pecan with either hickory or mesquite, but hickory, mesquite, and cherry? Hmmmm, can't help you there.
Rack choice: I usually smoke two meats at a time when I do brisket, something quick on the top rack like chicken or tri tips, the brisket on the bottom rack. I use a drip pan on both levels with a rack in the pan to allow full smoke circulation. I have smoked briskets alone on the top rack with the drip pan on the lower rack and never noticed any difference in color, smoke ring, or flavor between the two ways of smoking.
Smoke: Not having smoke on the meat for the entire unwrapped time will cause a very shallow smoke ring, or no smoke ring at all. Chips, even soaked ones, tend to carbonize quickly once they start smoking so you're going to get a lot of smoke for a short time. Chunks give you smoke for a longer time.
3-2-1 method: I'm assuming you mean you'd unwrap it at the end of the smoke to firm up the bark. Nothing wrong with that as long as you unwrap it at an internal temp and timing that will allow it to keep cooking without overcooking or undercooking by turn-in.
Give your method a try before the next competition and see how it works. Trial and error if often the best teacher.