The A7 has looong stretches with 120 and even 100 km/h speed limits, notably throughout most of Niedersachsen first leaving Hamburg, then between Egesdorf and Schwarmstedt (65kms), between Hildesheim and Melsungen (100 km) through the "Kasseler Berge" (that stretch used to be very fun to drive 30+ years ago with no limit and no traffic!) and between Aalen and Ulm (45 kms).
And traffic is actually worse than on the A9. The A7 is the central north-South route linking Scandinavia and Southern Europe.Tons of trucks, and in the summertime tons of slow-moving vacationer traffic.
Go on a Sunday (no truck traffic) and start very early to make the best of it.

Here's a map listing all the stretches of autobahn with no fixed speed limits. It's pretty accurate IME:
https://www.google.com/maps/d/embed?...9803115698&z=7