I've done my share of winter camping. BUT ... I'm always without running water. Water comes in several 6 gallon containers, cat-bath with water heated in a pan on the stove, and NOTHING down any drain or toilet. We have a port-a-potty. Dump it daily in the pit toilet (no chemicals), or use the pit toilet.
Although my current camper is suppose to have that "Artic Package", I believe that as much as cockroaches make good bed pets! I for one, don't want to risk frozen pipes or tanks.
About heat inside your camper. You may find the electric heater will not heat enough, especially with slides out. It's just too much space, and campers are sometimes just too exposed, with single pane windows and thin walls. If you find the space heater will not keep up, you'll need to use your propane heater.
We heat with propane, and supplement with the electric. We have 2 electric space heaters.
Another thing, take extra extension cord so you can plug in the space heaters at the campground power outlet box and not through your camper. Your camper may be able to handle 1 heater, but if you take a second, it might pop your camper breaker. (too much amp draw)... Just something to think about in the event you start popping breakers (either in the camper or at the power pole).... take some extra extension cord. It won't hurt to have it along as a precaution. I always carry a couple hundred feet of extension cord. Never know when it may come in handy.
One more thing, you need to leave a couple windows or ceiling vents cracked to allow air flow in and out of the camper. The cold air coming in needs to be heated, causing a higher demand on your gas or electric. WHY? you say??? If you don't keep your camper vented, you'll have condensation all over the camper in the morning. Windows will be wet and frozen, walls may be wet, blankets damp. It's just something that happens inside campers. By leaving a window or 2 cracked or a vent open, this allows ventilation to suck out the humidity that would otherwise condense on every surface you have.
Good luck and enjoy!