saving data on shutdown

Hi all.
I have a question on shutdown and the sd card.
As I understand it, when I perform a tidy shutdown ( I have a pushbutton set up to do this) the only data that volumio writes to the card is my settings data and playlist data before it enters standby mode. Any settings or playlist changes that I have made during a session would thus be saved. Is this correct?
My music collection is stored on a usb hard drive and so is safe.
In the event of a hard shutdown ( we get fairly regular power cuts where I live) would I just lose any changes as above or is it worse than that?
I do, as a precaution, back up my SD card at fairly regular intervals to hopefully minimise any loss of data.

Thanks for any advice.