I've just bought one of these android tv boxes and installed EMBY. The box is connected by wifi to my network and I have an ethernet connected media server that hosts the emby server.
I have emby on other wireless android devices (phone and tablets) that play backs fine. I also have a (ahem) plex server and the plex app on the Android TV plays back perfectly.
Any advice on the EMBY app, settings? is there more than one version (mobile/tv box).