on my laptop there is a Fn key combinasion to switch between them... btw i don't think it's possible to trigger this from the Os side of thing, it is tied to the firmware...

it's not there yet but in a few years from now there is hope, a vulkan driver is in the work and the nvidia signed firmware would allow power management for newer gpu, but it's not ready yet...

Btw it makes using other OSs painful when you are used to it...