In the Windows 10 version of the program, when I pick HDMI as audio output I am able to pick which Audio Codec will be passed through. This was very useful, because my TV is not able to deal with DTS and DTS-HD content but is very capable when it comes to Dolby based stuff.
In the Android TV version of the Plex app, I have no such choices when I pick HDMI passthrough. It does not seem to adhere to the supported passthrough audio formats from Android TV settings either, since the server send DTS audio as direct play even though both DTS and DTS-HD is disabled.