Hi again Larry
I'll try to answer some of your questions, but first I ought to say that 'Custom styles' are not an enormous reservoir of new rhythms; by far the larger collection of available style files from the internet will load into the Memory area of your Rhythms section of the keyboard (button immediately to the right of the Custom Styles button).
Regarding MSA I always have it set to 'Sound and Rhythm' but I suppose if it was set to Panel Memory it would then pick up any variations in sound selected by the producer of that rhythm.
Regarding Panel Memory settings 'expand' provides for the collation of all components of the registration someone has put together whilst 'Sound' only panel memorises the right hand sounds.
Hope this helps...
Rog