The RX 9060 has a TDP of 160W, but that’s the high end of what you can continuously draw from the 12v DC plug in a car, so it looks like they cap it at 100W. It has to be on the floor or under the passenger seat because it has to plug into that 12v outlet that’s usually in the front.
Things will get caught by the fan blades, and passengers will inadvertently kick it. Hopefully suddenly losing connection to the GPU won’t cause the car to hit a pedestrian or anything like that.
More generally, Comma's safety is handled by a microcontroller. The microcontroller limits steering torque commanded to a safe range for level 2 driver assistance and acts as a watchdog for the rest of the stack. Failure of openpilot causes it to disengage and sound an audible alarm.