I would definitely put a sealant on. A wax will be kind of pointless especially in the winter because they have the durability.
Sealant wise I would use sonax polymer net shield and get the quick detailer that matches, sonax brilliant shine detailer. The SPNS will last roughly 6 months and the BSN will keep it going long for when you do wash it.
I would also treat all your plastics, trims, and rubbers with a product to keep them moist and protected from the salts.
Another option is to seal or coat all your windows this it be good for year round but it will help you remove snow and help you see when your driving in rain.