A word of caution when your bike width is wider than your vehicle
We recently traveled from Virginia to Rhode Island and with two tandems on a hitch mounted Saris Freedom rack with the optional long wheelbase bar. The bikes are Hase Pinos, which have a shorter wheelbase than a typical upright tandem, but the overall length is about 8 feet. The bikes extended a few inches on both sides beyond the mirrors of our minivan. Driving back through Connecticut on one of the parkways with no shoulder next to the right lane, one of the bikes clipped an orange safety barrel making a very loud and startling sound. Fearing the worst, once we were able to pull off and take a look an inspection revealed no apparent damage. Though relieved, I was anxious as we continued through the dense and busy tri-state area.
This time last year we did a six week, 11k mile cross country trip with one tandem on the Saris hitch rack with absolutely no problems. Other than time in the LA area, we were in less densely populated parts of the country.
As for trunk mounted racks, for short distances, we have used a Saris Bones for transporting our upright tandem. It works fine though removing both wheels to reduce width is a hassle I'd rather avoid.
Other than the challenge of lifting the bikes onto the roof of taller vehicles, I am most comfortable with rooftop racks even though it exacts a significant fuel economy penalty. We also have a Draftmaster rack but it is for a larger 2 inch hitch and our current minivan only has the smaller 1 1/4 inch hitch. External transport of bikes involves a compromise of one sort or another.