I understand that it moves the existing files, not resyncs them.

Ok, I found a setting to enforce the sync mask for files already on the device, is that what you were referring to? So if I use that, what will happen to those files on the next sync? If all the existing files will have to be reconverted and downloaded it may not be worth the time. Thanks.

Depends on your settings. There is an option to enforce it for files already on the device.

If I change the file name structure in my device profile in MMW what happens when go to sync, will it only affect future files added to the MMA device or will it also update all existing files on the device? And if it updates all the existing files will it re-convert and download the whole playlist or would it only update as if the tags changed?

Thanks