The OP said the TT was insulated for winter. That can mean a lot of things but, if it is and the tanks are enclosed and heated it should be fine. As was mentioned, sometimes the dump valves are not enclosed. If that's the case, dump some RV antifreeze into the holding tanks when they are empty so the antifreeze gets down to the valves.
Electric hookup is the most convenient winter option but, not necessary. My Arctic Fox has storm windows which really help. We camp in winter at temps to below zero and use the entire water system. I have no trouble keeping the temps inside at 70 during the day and turn the heat down to 60-65 at night.
Fill your FW tank during the day when the sun is out and then disconnect the hose and put it where it won't freeze. If camping without hookups, you will need a minimum of two, big batteries and a generator. You'll have to run the generator at least a couple of hours every day.
Had a class A some years ago and dry camped almost every weekend in winter. Had storm windows, (which I made), 4 batteries and ran the generator a couple of hours every day. We were always comfortable and everything worked.
Going every weekend I kept the MH at home and plugged in with the heat on low. The TT is stored elsewhere and only used a couple of time per winter so I winterize. Doesn't take that long to blow out the water lines and put in some pink stuff and then flush it out when it's time to go.
In Colorado there are a lot of commercial parks that are opened year around and some state parks. All have, at least, electric. Winter is a beautiful time to camp.