This was late May near Mount Rushmore. Weren't expecting snow!
Our A/C had a heat strip, and we used a propane heater too. Zero insulation on a Popup, but inside temp was in the 50s. In the mid 20s at night. No outside tanks or plumbing, so that wasn't a factor. We had a porta-potti, and used the campground facilities. Nice thing was there were plenty of campsites to choose!
Our last TT had exposed tanks, and I ordered it with tank heater pads. Basically a peel and stick product. It's wired into 12V, and is rated for the temps you mentioned.
We did take this to North Georgia, and had freezing temps overnight. The campground required all water hoses to be disconnected before sundown. The truck had frost the next morning.
While we had no problem with the tanks, my propane regulator quit at 0 dark thirty. The camper was cold inside, we could see our breath. But I always plan for contingencies. I plugged in the 1500W ceramic heater and we went back to sleep. That had no problem keeping the camper warm. Turns out the first propane tank emptied due to using the furnace, and the shuttle valve stuck halfway when switching to the other tank. Couldn't use either tank, didn't have a spare regulator. But as luck would have it, there was a Camping World not far away. Picked one up that day, good to go.
Our current motorhome has tanks inside the belly of the rig. It uses air from the furnace to warm the tanks, and has the same sort of heating pads as shown on the travel trailer. Hoping we make a cold weather trip sometime soon. "Cold" is a relative term to those of us in FL.