You can stream Hi-Res music through Audirvana but we don’t recommend Air Play to do this since you won’t be able to go higher than 16/44 which is not Hi-Res.
If you are using UPnP you can stream whatever quality of music you want, even DSD if your DAC have this feature over UPnP.
How to know if my device is available in UPnP with Audirvana? When you select your output you will have two sections, one for the local connected DAC (internal, USB, SPDIF,etc…) and a second one for Network connected DAC. You then need to select your DAC in Network area and play your song in Audirvana.