The first answer for you is; Where will you be camping and how Cold does it get there?? The projected temperature will control all of your decisions.
With that said, when I "Winter Camp", I use several of my heating tools in combinations that make sense for me.
1- When I am using a campsite, with Electric hookup, I always keep an electric blanket on our bed.
2- Because I have my blanket, I always set my RV furnace down to 60-65F at night.
3- We have a good safe ceramic electric heater that we will plug in at night in the living area, and set it for the same temperature as the furnace. We shopped around and our heater has several safety functions such as being "UL Listed" and a "tilt-over" turn off capability,
4- Also, our roof Air Conditioner is actually a Heat Pump, and we use it in that mode because our temperature control panel will automatically switch over to the Furnace for heat when the temperature drops below a certain point.
5- As to your water lines, if you are going to be camping in very cold weather, you need to look at your Holding Tanks and water lines as a separate issue.