the element will produce over 300 f, though in my experience with my pid set at 350 for 6 hours the smoking chamber hard a hard time getting to the low 300 f maybe 325 and this was on a 75 f day, and the top vent was wide open so excessive temp i dont think is an issue, the only concern would be a fire,. if proper installation is done and no grease gets on the element you should be fine.
if your pid fails most likely it would fail to the off position, meaning that the heater would be turned off when the pid fails.