cold weather travel and residence are difficult topics. They are so dependent on your unit build, use and proactivity..
Most units with enclosed water, both fresh and waste, with heat on in the unit while traveling in temps above 0 f should be fine. You burn some propane while on the road. Both safe and legal.
We do not know your unit build, so, I would say if your unit is enclosed amd systems heated, take your colder route, or if you are concerned go the long warmer way.
We have many times left SD with our 5er for the south or returned in much colder temps than you forecast. All was well.
. Another thought, cant you find a local rv pro to give you guidance on your rig?