Towing on snowy roads

In Washington, a 4x4 locked in gear does not need to have chains unless the signs are out for trucks to use chains. You must carry chains! Normally you would install when required on the rear drive axle and on the last braking axle of trailer.
https://www.wsdot.com/winter/tires-chains.htm

I work on Donner summit in the winter and see RVs (but not many) going through chain control. Also most 18 wheelers do not park they chain up. As for your set up you can put good steel chains on the back wheels for better traction. Your trailer get a good set of cable chains. On Donner summit California 1-80 they won't let you through with our chains on truck and trailer. If was me I would wait out the storm!

Most passes are cleared well to maintain travel, cross when clear. If chains are required find a place to park it's not a time to be driving. No reason to drive in that kind of weather, most 18 wheels park and they drive thousands of miles a month.

Tuna’s advice is excellent! If the law isn’t specific, I chain the rear wheels of my 4x4 when towing...and the TT. If not towing, I chain the front.

Do what the law requires.