My next thought was to try the the GPU selector that Microsoft added in 1803...
Whoa, I never paid any attention to this feature but it seems to work just like
Lucid's Virtu. I just tried it out by enabling the Intel iGPU on my desktop, moving my monitor connection from my discrete GPU to iGPU, and then making sure the iGPU was set to the correct power saving GPU option.
Interestingly, I found that
you don't need an application with a rendering GPU option in order for this to work. I manually set a game (Pillars of Eternity II) to use the high performance GPU and started it up to see what would happen. To my surprise, it worked as intended.