I am unaware of the advanced simp reps you are referring to. We have never had AAX, and I have always been able to create as meany exploded states as I like. I just wish the exploded view linked to a view orientation.
As far as I know, one can create drawing simplified reps in drawings, interchange assy, skeletons (tho we have a decent work around for the skeleton), copy geom, publish geom.
There is likely more that I am missing as well. I wish I had interchange assy. Work arounds for this lack of functionality are quite tedious.
AAX provide many more advanced capabilities in driving and managing assemblies and complex designs. E.g.Interchange assembly, Unrelated Replace, Default envelopes, Motion skeletons, Inheritence features, Shrinkwraps, Reference control and viewer, manipulate assembly Pro/PROGRAM, assembly UDF, etc.