I Directplay all my Videos on Nvidia shield this connected via hdmi to the TV and the TV has extern 2.1 Sound System.
It would be nice if you could adjust the volume like in Kodi.
Sorry for my poor english.
Let’s assume for a moment not everybody is familiar with how Kodi is doing it…
What specifically are you asking for? 
Sorry 
In Kodi you can setup the speaker configuration (2.1, 5.1 etc. pp)
Id would be nice if the plex android player can this also.
And in Kodi you can set the Volume output higher as the TV (Volume 100%) can.
