I'd have to disagree about "without any traffic jams ever" on the autobahn. We spent only 3 days driving in Germany, and of that time, about 4 hours was spent sitting on dead stopped autobahns, especially around Hamburg. Didn't seem to be any shortage of traffic jams in that area.

As for renting a car in one country and dropping it off in another: we needed to do that, and found by far the best rate was with Hertz. The base rate was higher, but by booking it through AAA we did not have to pay a drop fee, so in the end there was a considerable savings.