I have a playlist which I sync with my clip+ memory card (using the path Sansa Clip+ 4GB\External uSD Card\Music\) but whenever I reconnect the device with only a few changes to the playlist, after it detects which albums I've removed, it continues to copy every song on the playlist to the clip again, including those that are already on the card.
The settings I have are 'detect mtp', 'automatically sync', 'do not copy artwork' and 'delete tracks that are not on the auto-sync list'.