Boneless turkey breast is one of my favorite things to smoke and I've probably done that more than anything else except pork butt.
High heat vs low and slow - I always do mine low and slow, but the caveat is that I use boneless, skinless breasts. So if yours is skinless, I would say go ahead and cook it with your pork. If it has a skin, high heat will give you a better chance at nice crispy skin.
Brine - I don't brine mine...but again there's a caveat: I've been using "enhanced" breasts (i.e. injected with saline) so extra salt is not needed. Instead, I just rub with something I call "Southern Willy" which is basically a combination of "Southern Succor" and "Wild Willy's Number One-derful Rub" minus the salt:
Southern Willy
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4 Tablespoons paprika
4 Tablespoons ground black pepper
2 Tablespoons turbinado sugar
1 Tablespoon chili powder
1 Tablespoon granulated garlic
1 Tablespoon onion powder
1 teaspoon cayenne
I have had tremendous success rubbing the enhanced, skinless, boneless turkey breast with the above and then cooking low and slow. The turkey is incredibly moist and has tons of flavor.
Hope that helps.