I've got a Roadtrek Class B and I flat tow a 2-dr Jeep Wrangler with it. Have over 20,000 miles of towing without any problems. Have gone into the Rockies twice and made a trip to Alaska with this combo last summer. Almost like there's nothing back there and the only hit I see is on gas mileage - towing I get between 11.5 and 12.5 MPG. The 2dr Wrangler is about 3,700 lbs.
If you're looking for a lighter weight toad you might consider the Smart, Mitsubishi Mirage or the Chevy Spark. All three would either need to be trailered or dolly towed though. The Smart is 1,900 lbs, seats two and uses premium gas. The Mirage is 2,100 lbs, seats 5 and uses regular gas. The Spark is about 2,200 lbs, seats 5 and uses regular gas. All three get around 40 MPG and could be trailered on a single axle trailer; the Smart on a 10ft, the others on a 12ft and this combination would bring you in at about 3,000 lbs tow weight.