The AAMC material is not comprehensive, but you should spend a good deal of time ensuring you understand everything they ask about. In my opinion, this is where the third-party materials do a good job of filling the gaps. Although the third-party material won't be as representative as AAMC material (although in my biased opinion, Next Step does a pretty good job!) they will be more comprehensive in covering more of the topics.
If you're interested in trying out some of our material, I have a link to our free practice bundle in my signature! The AAMC material is the most important stuff there is and you should complete all of it before your exam, but since it's not comprehensive, I do recommend supplementing it with some third-party material as well! I hope that helps and please reach out if you have any questions!