[p750mmx]

Windows 10 is my OS; In the configuration of the listed supported Codecs, I don't see Dolby Atmos or DTS:X listed.
If a file is played with either codec, will it just passthrough the data and have the Receiver bitstream properly or will it get downmixed to something else.

Should there be updated drivers to support Atmos or DTS:X?

With the (leaked Final) Windows Creators Update the Dolby Atmos addon can be installed through the app store (only after installing the CU), but Kodi (17.1) still doesn't play Atmos as is. DTS-X it does although its not listed as a supported format under the Windows audio formats. My receiver shows Atmos as a Windows standard audio output after installing the Atmos addon.