Z10 Pro - flac or cd iso

[foetus]

I am planing to rip CDs for my wife, music player has nice and simple interface for her to use. What are your recommendations? I have 4Tb WD Red in bay. Should I do single flac or cd iso? It is small collection of around 200 CDs. Z10 Pro is connected to Denon AVR-X1200W and we often listen music in All Zone Stereo mode (living & bedroom/reading room). I use Spotify Connect but she is more CD person.

[futeko.com]

FLAC. Ripping CDs to ISO (wav?) would give much larger file size for no quality gain.

[foetus]

Thanks!