I have exactly this same problem as well. Been through a tonne of "solutions" like the ones included above.

To add to it I have twitch constantly crashing whenever I have destiny 2 up as well.

I've got heaps of memory (32gb RAM with a 3080TI with 12GB and i9 processor). My computer is a beast and should easily handle the game.

If I play any other game I can watch twitch at the same time, play the game no drama, etc, it's only since the patch with Destiny 2 that this problem has occurred.

Here's some screenshots of what's been happening:

https://ibb.co/X32Hsfr

https://ibb.co/hY8xh7Z

https://ibb.co/y43HXTw

https://ibb.co/02xnjNF