All the songs I have copied to iTunes get uploaded, but if you have the lossless versions they get converted to normal quality on other devices, or if you remove the local original copy.
Music doesn’t support flac, though, you have to convert them to alac first.
I also use a Mac, I don’t know if it’s different on windows
The nice thing about the fediverse is that you could start your own instance and not federate with them