It doesn't hurt to copy playlist, database and tags files. I have done so when upgrading my player, and I've omitted the "empty sync" step (which rebuilds these files from the fids).
If you choose to copy config.ini, you should do this at the same time as the fids and the above-mentioned files. Definitely before you make the destination drive read-only again.
Copying the dynamic data partition can be done at the same time. It is possible to leave it until later, as this is writing directly to the partition, not to a filesystem, so there's no concept of read-only for this part. (Indeed, this is why a raw partition is used, so that the player software can write to it whilst the filesystems are read-only)
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Toby Speight
030103016 (80GB Mk2a, blue)
030102806 (0GB Mk2a, blue)