The internal temp doesn't really matter. Quality of meat, cooking temp, etc all impact the proper time to pull a brisket. When a probe goes into the thickest part of the flat like butter, it is done. Higher quality meats will typically be probe tender far earlier than cheep ones. Very slow cooked will also come off at a lower temp. There is also the issue of how long to rest the meat. Faster cooked brisket will need to rest a little longer to relax the muscle after coming off of the smoker.