I imagine that the Training Guides for MYOB Premier Accounting & MYOB AccountEdge would also work for FirstEdge, just with additional info right?

I assume that you mean the manual for various version of MYOB. Every version has its own strength and limitation. The higher end is more sophisticated and need more learning to fully utilize it.

Just for the job of downloading bank statements, various versions of MYOB would do it differently, you can read the discussion on the MYOB Premier forum.

I've been doing accounting for a long time, and recently I've bought a Mac and various versions of MYOB software just for the sake of learning the differences and limitations of the various versions.

My answer to you is, no. You can't rely on the manual for one version to work on another version of the software.