Note that this option is only useful for devices that do not have their own databases with Playlist support. By enabling this option, playlist files are copied to a specified directory on the device for each Artist / Album / Playlist that is synched so that you can play any set of tracks by playing the playlist. Note that some devices do not support .m3u playlists.
Tracks will sync to the device per your configuration.
If you want to do a one-time manual sync of set of Tracks:
The selected Tracks and Playlists will sync to the device per per your configuration.
To simply copy tracks to a device without using synchronization functionality, use the Send To > Folder (My Computer) option that is available when right-clicking any Track. This will only work for USB Mass Storage devices.
MTP devices can be unplugged as long as data isn't being actively transferred. If you wish to play it safe, or if you're using a USB Mass Storage device, MediaMonkey can be configured to automatically close the connection to the PC after synchronization. If this feature isn't enabled, then right-click on the device and click 'Safely Remove Device'.