For a week or two at hunting camp, if you accept no water system, just about any trailer will do fine down to the teens (yeah, you may go thru quite a bit of propane if it's down in the teens). Just winterize the water system and leave it alone. (I prefer the pink antifreeze as it's easy for a bit of water to sit in a low spot waiting to freeze later).
The other stuff comes up if you plan to spend the winter in the rig. At that point, living without a water system is a much bigger issue.
Yes, a lot of it is marketing. Look for features not an arctic rating (underbelly insulation, heated underbelly, heated waste tanks, double pane windows, etc...).
You mention generator. I would be careful with that. If you run out of fuel in the middle of the night and you are using the water system, things could freeze up before you wake up.
