There are multiple correct answers, so don't take anything I say as a statement of it being the only way.
I have always wet brined my briskets. One of these days I may try a dry brine as I hear wet vs. dry results in different texture. I've always purchased full packer briskets, though when I had my #2 I would cut them in half and smoke both halves on separate shelves at the same time. So, technically, I've never smoked just a flat.
I've never injected anything and don't see any reason that will ever change. I don't personally think it's necessary at all in these smokers.
For temp I have most commonly done 235, but there should be no harm in going at 250. I have never wrapped and this is also something I have no intention of changing. Using a pellet pooper or stick burner you kind of have to wrap because the pellet/wood combustion is sapping moisture. The Smokin-Its really keep a humid environment (especially if you include a water source up next to the fire box) and the temps are pretty stable, so you don't need to wrap. In fact, opening the door just lets out heat, humidity, and smoke in addition to making you work more. I recommend throwing it in and just ignoring it until you hit your target temp.
Your 200 deg target temp is a good place to check whether it's done. In addition to the probe passing as if in butter, the whole brisket should jiggle like a bowel of jello. Ultimately it is done when it's done regardless of temperature. I've had some briskets that didn't even hit stall until around 200, so that's not an automatically safe temp at which to pull it.
