1) If I were doing a high ticket/Snake River Farms brisket, I would absolutely pull the splitter, (which takes seconds) and put the meat dead center with foil and drip pan on the lower grate.. The heat left, and right sides of the meat would be completely uniform..
If you want to leave the splitter in I'd still put the meat over the coals with foil to make your airflow indirect.. Might not be noticeable but with the splitter in and the meat on the other side the far side will be a lower temp.. Not sure if it will change the outcome in a noticeable way but one side will definitely get more heat. Note.. All offset cookers have directional heat and they get great results..