I gotta say, I do mix and match, but I do keep in mind what Susan has said about common themes/moves running through a release...
e.g. on some of the releases a move in the Tai Chi & Yoga track may be used again in the Release & Restore - so I would use both of those tracks, and so on with other tracks...
So, where I do mix and match - I'll only swap out probably 3-4 tracks max from a release, but do 8-9 tracks from the same release to maintain the common theme...