You will not get indication of bit perfect transport. And the output method always will be the OS Mixer. This appears not an official solution for Chromecast Audio support, just a kludge that is capturing the entire system audio of the OS Mixer and casting it. That system audio of the OS Mixer can be bit perfect – if no processing is applied to the audio and no other system audio intervenes. But no indication of bit perfect output is possible.
AJ