I have towed with both a trailer, with a 2-wheel car hauler and with an old VW tow bar. I had problems with the car hauler as the U-Haul people had not checked the equipment correctly and the straps kept coming loose and required frequent checking. I never had any real issues with the tow bar. I drove from Wichita Falls, tX to 29 Palms using the tow bar, from Owensboro, KY to San Angelo, Tx with the trailer and from Arlington, TX to Reedsville, PA with the car hauler.
I drove my 70's Ford pickup about 70 mph all the way to 29 palms with the car in tow and that was essentially the speed limit back then in the 70's. I actually had an axle key way break in NV and had to pull over at a motel and spend the night. I was about ready to cry as there wasn't anyone with a replacement on a weekend like that and I just knew I'd have to abandon the car. Well, the say that God protects fools and drunks and when I got up to go outside the motel room the next morning, I spotted a hot rodder who was tearing a coupe apart in his front yard right across the street from that motel. He told me I could have anything on that car for $5 bucks and I bought another keyway to replace the broken one. I didn't have room at all to pick up any of the parts he was offering though. :-(
When that key way broke the wheel came out of the axle housing and it looked like something from the Keystone Cops as it went in and out as I sped along. I saw it in my rearview mirror and you never saw anyone apply brakes as hard a sI did that day to stop before the wheel left the car. It was a brown shorts moment, for sure.
I bought a '36 Ford coupe once that was stored along a railroad track. My father-in-law and i decided to tow it behind his '54 Chevy pickup with a long chain. Well, the coupe didn't have a seat in it and i had to sit on a Coke soda water box and guide it as he pulled me down the road. We only had a few blocks to go, too. Well, as fate would have it, the steering wheel pulled off in my hands and the car started going where ever the heck it wanted to go. He was more intent in looking forward and didn't notice until he saw me trailing behind his pickup and running through some lady's flowerbed out of control and holding a banjo steering wheel out of the door and waving to him as I hollered for him to stop. Another brown shorts moment, for sure. Like a real dummy, I later sold off that same coupe to purchase books for a college semester. You would laugh if you knew how little I asked and got for it back then, too.
Me, I would say to be careful no matter what method you choose. Don't rely on anyone to check your safety equipment. It will be the inattentive person behind you that makes it most unsafe to tow a vehicle these days, but for long distance hauling I'd choose a trailer over all the rest, just because it seems more secure and you can add brakes. An enclosed trailer is likely even more secure, as no one is likely to enter it and ruin or steal anything most of the time.
Good luck on your trip and your choice. Take photos and share.