Wrap at 165 degrees. No to injections - if you must, mix beef broth with worchestershire. You can rub right before cooking or the night before. Won't make much difference. Let it REST, wrapped, for at least 90 minutes after it reaches 202 (very important). Salt and coarse ground pepper is a great rub. Consider adding some garlic powder and chipotle or cayenne to make it more interesting.

Yes, you can cook it without wrapping. But wrapping is safer for newbies and won't hurt the flavor at all on a pellet smoker. I've cooked probably 100 briskets, 1/3 without wrapping and 2/3 wrapping. These days I wrap in a "foil boat" with foil wrapping up about half way with the top exposed. I think that is the best of both worlds.