Hello and welcome to the Langshan thread!
As for wintering abilities, I had my birds up in PA (after travelling to OK). They did great up there! I hated every minute of the snow after the second year. The cold was different than that of Oklahoma's winters and I never seemed to have an issue of frostbite up there.
So, I will go with what I know more of. In OK, the weather can change drastically. It would be 58* one day and the next -10*. The birds do amazing in weather changes but be prepared for sniffling in those extremes. A shift like that can cause some reactions.
I prefer to breed for smaller combs thanks to the cold. It cuts down on frostbite and thereby makes me have to be out in the barn less to prevent it. Some birds have larger combs and can get frostbite however I have not had a single bird lose more than the tip of the points, whereas my bantam Speckled Sussex lost the end of the blade and the points to the comb.
I have never had a Langshan lose toes or wattles either. They are not big fighters so keeping them with birds that are more aggressive is not the best idea. They will put birds in their place but are not ones to pick fights normally.
As for free-ranging:
I always keep my birds in outdoor pens. I don't like to chance a predator taking a bird and then deciding to come back for more free food. I have hawks routinely pass over the cages and apparently think better of taking one. Is it their size? I can't be sure. They are just as susceptible to predation in the coops (raccoons, possums, etc.) as the other breeds so having a secure coop is needed. I have not lost a Langshan to a snake so that's a plus side.)