Tom C 47,
Forget the Arctic Pak heaters. They are only on the black and grey tanks. Just leave those tanks empty. The Arctic Pak heaters aren't of much use. Although they heat the tanks, there are no heaters on the drain lines and valves, nor on any of the fresh water plumbing. That is all vulnerable to freezing.
On Sunseekers and Foresters, the tanks, water filter/pump compartment and sewer drain compartment are heated by ducts from the propane furnace, so the Arctic Pak heaters aren't needed. Just run the propane furnace on a low temperature setting to keep the coach above freezing. That will keep the plumbing and tanks nice and warm. Since you are plugged in you won't have to worry about the furnace draining the batteries. Be aware that an electric space heater will keep the coach warm but won't heat the compartments or plumbing.
Also, if there is water in the water heater, drain it or leave it on. The propane flue is submerged in the water and it conducts heat out of the water, so the water could freeze if it stays cold long enough. If you have enough amps available, leave it on electricity instead of propane. I'd just drain it. Be sure to turn the water heater's 120 volt breaker off so you don't inadvertently turn on the heating element with no water it.
2011 Sunseeker 3100
2016 Ford Edge Toad