Cycle - I have travelled in temps down to -25F.
I drain and winterize then flush the toilet with rv antifreeze.
I carry water in jugs in the heated camper.
Carrying water and waste water in the tanks is fine if you are sure your camper can keep its basement warm.
There are charts available on line which will show you how cold a tempurature your propane cyclinders can supply vapor to the furnace before they need additional heat to keep the propane boiling.
Propane cylinder filling is available all through western Canada in winter.
Oh and cold air is dense so takes more hp to overcome aero load - up to 30% more at -20F. And if your truck is a diesel winter diesel has 20% less btu/lb than summer fuel. Fuel economy will be less than summer travel.
Have a great trip