Sample rate/format

Can anyone explain the sample rate and format at various stages in the chain from airplay to output via is2? And is that preferable to using USB?

I would like to find the cleanest way to play via airplay and output digitally to an external DAC. I’m thinking of using a justboom Digihat rather than USB, but I’d like to understand what happens up to this point in converting airplay at 44.1 kHz ALAC and outputting it to IS2 - does anyone know? Does volumio convert to a different format or rate? Does the digihat carry out any conversion itself?