Apple storage pricing is pretty fair and the delayed deletion is a benefit to most. The issue is the walled garden. /e/OS behaviour in Music file sync would’ve created a similar quota problem.
As to Flacbox and local music streaming: I found subsonic (a protocol, see apps that use it) to have improved streaming habits at home, but it depends on the existing device zoo if there’s a natural place for you to put all files others stream from. Takes cloud out of the equation though.