[LongMan]

1. In the cast menu is shows 2 instances of the kodi box, one suffixed with kodi and the other with DLNA. Which one to choose for better/ loss-free playback quality?

Unfortunately, I cannot help with that one. DLNA is disabled on my server as I don't need it. I think Kodi plays the file directly.

2. In remote control mode does the audio get routed through the phone and then cast? Or does it act as a pure remote control? Latter is preferred.

The latter. If you disconnect while it is playing, it just continues. I think it sends a playlist to Kodi and Kodi plays it. Once it is playing you can use the remote control feature of the client to control it. However, from Kodi it is the same as starting the item from the GUI.

Hope that helps.
Cheers,
LongMan