I don't know if there's a programmatic way to enter Xbox mode when starting a stream except by navigating through the Windows UI.
Also it seems to get the performance benefits you need to reboot directly into Xbox mode to prevent it starting unnecessary processes, if you switch to it from the desktop it leaves everything running. So that's disappointing.
I suppose if you really like the full screen task switcher, that might be something.
u/Full-Mud3709 — 12 days ago