In my experience actually PAX drivers didn't solves audio issues with Z170X Gaming 7. Also Op-amp it is not the cause of broken audio (anyway this is a few cents $/€ component).
After a lot of test I found that there are some compatibility issues about Creative audio drivers. I found a lot of errors related to Creative drivers into the Windows Reliability Monitor. It seems that Creative drivers are not fully compatible with Windows and other audio devices.
I made test with RC1, RC2 drivers provided by Gigabyte and different versions provided by Windows Update. In my case I found this work around starting from a fresh Windows 10 installation:
- install Creative RC2 driver version without optional stuff (only drivers and control panel).
- install AMD graphic and hdmi audio driver provided by Window update (I have a R9 Fury)
- install last AMD drivers without updating AMD HDMI audio drivers
- deactivate "Turn on fast startup" option (https://www.cnet.com/how-to/what-is-windows-10s-fast-startup/
In this way I do not have errors into Windows Reliability Monitor and my audio issues dissapered magically. If errors appears maybe some driver was overwritten (in this case rollback it) and try again.
I opened a ticket to Gigabyte support and they published 2 new driver versions in the while. I didn't made test with these 2 january driver versions provided by Gigabyte to avoid brokening something. I'm waiting that PAX will give a look to them before.
I suggest to you to give a look to Windows Reliability Monitor before attempt any action.
As a rule for the future I will avoid to bought any motherboard with Creative audio chip. Only Realtek...