I have been to Germany and I have driven the Autobahn.
Yes, there are limited and unlimited zones. The limited zones are strictly enforced, but, really that's mostly unnecessary because for the most part Germans follow rules no matter how silly the rules are.
However, the limited zones in Germany are often set at a much higher limit than would be the case for an equivalent zone in the US and in many cases, the limits in those zones are enforced more by the laws of physics than the landespolizei.
Yes, accidents in the unlimited zones are often spectacles of carnage due to the KE involved, but, they are also quite rare.
Speed doesn't cause accidents. Differential speed causes accidents. On the autobahn, every driver understands that if the car behind you wants to go faster, you're too far to the left and you should move to the right. If you think you get pulled over quickly for speeding in the limited zones, you should see how fast people get pulled over for failing to yield in the unlimited zones. That's because the Germans understand that the guy going slow in the fast lane is the real source of disaster, even if the faster driver manages not to hit him in the process of the collision he caused.
In the US, generally, this accident causing party drives off oblivious to the fact that he caused an accident and is rarely prosecuted for his non-contact hit and run.