I think the first thing to do is determine what plumbling is outside the heated areas of your camper. Is the fresh tank underneath the camper frame or inside under the bed or sofa, etc? Do u have any water lines running below the camper.
Our previous TT also did not have an insulated or even covered underbelly and all three tanks were mounted under the camper, but all of the water lines were inside. We were able to camp thru mid Nov here in Michigan, by draining everything between trips and making sure the camper is up to temp before filling with water.
I guess it also depends on the kind of camoping you will be doing. We've stayed at full-hook parks that provided a heat traced water supply so all we had to do was drain the connecting hose at night if the temp was expected below 32.
When relying on the fresh tank for water, we never had a problem as long as the temp did not go below freezing for too many hours. With the camper warm (68-72) it provided enough protection to prevent the tank from freezing...
However on one occasion, we had a wicked overnight cold wind with temps in mid 20's and the tank partially froze. It eventuaslly thawed about mid morning when it got in the upper 30's.
You can add 12 volt heating pads for your tanks...I have no experience with that but I'm sure others here can offer comment.
The bottom line is u just need to be careful, know hetre you plumbing is and keep an eye on the Temp.
Cathy & Jeff
2020 Cedar Creek 34IK / 2019 Ram3500 CID