Thanks to everybody who offered suggestions on this. I have found, through experimentation, that to achieve the result I want, shuffle all albums but play songs in album order. Repeat "Advance Category" and Shuffle "Shuffle Categories". That does the trick for me.
I found "Repeat Advance Category" a confusing term since it doesn't really Repeat but rather Continues to play songs within the Category.
Anyway I've got the result I want and have now purchased the Unlocker to continue enjoying Poweramp beyond the trial