Jay, I just use the lid temps mostly as an indication of how the internal temps are trending and just a rough estimate of the true internal grate level temp. I have watched my lid temp compared to my grate level temp with a Thermoworks Smoke thermometer at grate level, I am pleasantly surprised at how close it is when the temps are stabilized. But the lid temp is slow to catch up during fluctuations and for something like ribs, brisket, and these Rib roasts, accuracy is a premium. So, if you go by the lid thermometer, first, verify how close it is to actual internal temps and second, realize that it will be slow to respond bot right after you open the lid and then close it again.
With the Thermoworks smoke ambient probe at grate level, I would shoot for 275 and try to keep it within ten or 15 degrees of that during the cook. And I also recommend an instant read internal thermometer for the meat itself. 5 degrees up or down from the desired doneness is a big deal. At those temps the outside of the meat should form a nice light crust and look very appetizing. But, if you like, you can sear it the last 5 degrees or so to add to the crust. But, I would play that by ear and if it looks good when you are approaching your desired done internal temp, if it looks good, then just let it ride until the desired temp is hit. I also suggest to limit the opening and closing of the lid as much as possible during the cook.
