Please make a Windows restore point prior to fiddling with the driver settings !
If you want to switch to using Realtek drivers then then you might end up having use for the Realtek Audio Control , if not already on your computer then from either Microsoft Store or from a driver download from computer or motherboard manufacturer. Also , using Realtek you might have to go to the Sound Control Panel (found right side menu of Windows Sound settings) to make some choices of sound settings !
No, you'll need to change the audio device in Kontakt itself under settings/options -> Audio.
On Windows it's File -> Options
So you'd want to pick the Realtek device in this case. I don't have WASAPI drivers loaded, so that's why the screenshot shows ASIO, but use whichever one works better for you.
It might work generically? Definitely worth reinstalling the latest drivers from your motherboard's support page.
What reffahcs wrote ! My advice regarding the Windows Sound settings were a general one directed at the overall sound use on your computer including for when wanting to use digital audio ! (as written then make a Windows restore point prior to changing Windows drivers and sound settings !)