On the server machine, I only have two playback devices listed:
Speakers – NoMachine Microphone Adapter
Samsung 4 – NVIDIA High Definition Audio (Default Device)
There are no other devices. If I choose “Show disabled devices” it offers up the unused S/PDIF connection on the motherboard. The server machine is using the HDMI connection on the video card to output audio and video to my TV and Surround processor.
I don’t connect more than one client simultaneously. I just move from work machines as clients (Windows 7 and Linux, to remotely access my home machine) and my laptop client at home (Windows 10) to move about the house.
I’ve attached a short audio file of an attempt to view a video over the LAN from the server to my Windows 10 laptop client.