P setting regulates the time between augur activation. If it is running below the temp you set it to, lower the p setting. If it is running hot, raise the p setting. That said, the cooler it runs the more smoke you'll get and smoke production drops off with higher temps. You can play with it by running at a lower temp and lower p setting to get it to produce smoke more often. On the smoke setting it should be running 120-180F depending on the ambient temp and p setting.
With pellet grills not producing dense smoke above 225F, it's recommended that you utilize the smoke setting to run a low smolder for the first 1-4 hours and then crank the temp to actually cook the meat. 250-300F is good for brisket. I believe Aaron Franklin does his at 285F. Wrap when the internal temp hits 160-170F. Your finish internal temp is going to be 200+, could be 203-208F, whenever it is probe tender. Cook with the fat cap facing down to protect the meat. Contrary to popular belief, rendering fat is not basting the meat if you cook fat side up.