Firefly is a ‘read only’ application. It doesn’t move or reorganise your music.
It simply makes your iTunes library available to other network attached devices without the need to have iTunes running.
You need to use iTunes to do the things you want. Firefly is just the equivalent of the ‘share my library’ tick box within iTunes.
The advantage of Firefly over iTunes is it works with more operating systems & doesn’t need a PC/MAC to be running
Firefly will pick up changes to the library when it does a rescan