You don't need to worry about the Nvidia audio being named 'Unknown' in DPCIManager. It is a cosmetic issue.
You need to look in System Information and the Audio report to see what is showing up.
Here is a screenshot showing my Audio tab/report as an example of what you might see.
Your main audio for your system is the Realtek ALC1150, which is accessed via the ports on the rear I/O plate on your motherboard.
WhateverGreen.kext and Lilu.kext should make your HDMI audio work, if that is what you are using. However you will have no volume controls for the HDMI audio within macOS. Not unless you install a third-party Audio app. All HDMI audio is controlled on the display/TV you are using.