I've had the kaby xps 13 for a few weeks now. Great laptop!
However, there are a lot of confused people around the internet regarding coil whine. The issue is actually with the realtek audio drivers and power management. I know it sounds crazy. The laptop with no drivers makes an awful noise, like an old style mechanical hard disk. It does indeed sound just like coil whine. Installing the latest realtek drivers stop this, but introduces another issue. That is whenever a sound is played through the audio card, it comes out of power management and makes a loud pop. When it enters power saving again, it makes another pop. Very annoying!!!
The fix is either:
Contact realtek and get them to email you the driver without the power management
Download a third party program which runs as a service to keep the audio card channel open
Dell issues don't stop there though.....the usb-c port is rubbish. It's not a dell thing, usb-c ports in general aren't great
Dell WD15 usb-c hub has a design flaw which can't be fixed. If you buy one, send it back for a refund quickly.
No usb-c hubs will simultaneously charge the laptop whilst displaying an image to a connected monitor and work the usb hub. This may be down to the laptop itself and the implementation of the usb-c port.