For a toyhauler the one that comes to mind is the Excel Wild Cargo. If not a toyhauler then DRV, Lifestyle, Excel.
You have to realize that even a well insulated 5th wheel is not as good as a house. Wind gets under the floor of a 5th wheel if you do not block it with straw or something. Also the walls are not as thick.
Trailers get cold spots in corners and cupboards.
Also it is difficult to find an RV park open all season as above ground water hoses and spigots will freeze.
There are people that do it so it can be done.