I have the same problem, also with the AMD RX 6800XT.
Sorry to say I have no solution. I’m looking for one, just like you
It stops when I’m in the game settings or when I tab out of the game. Similarly to what you describe, it doesn’t matter if I lock the fps to a lower fps. The coil whine is always there.
This is a card issue. Coils will whine if under extreme load and are not orientated precisely or made to exact quality standards.
They can whine on PSUs, GPUs, etc. And its completely dependent on quality and manufacturing.
If you get coil whine, you have three options:
Reduce the load.
Deal with the noise.
RMA the hardware that’s causing it.
I should note, that a PSU not producing clean power (or having issues with power delivery) may introduce coil whine sometimes too when card is demanding high power use.
Out of curiosity, who made that RX 6800XT.
First off, I would get that card and powersupply tested as the card could be an issue or the powersupply, or both. Once you know if it is the card or powersupply, get them RMAed, or replaced.
I had some odd lockups on my MSI RX 7900XT, until I uninstalled the High Res Texture Pack. Coil whine, I haven’t had.
One way to reduce the load on the card and your system, is to uninstall the High Res Texture Pack.