The first option seems to be misnamed. When it's disabled it will cache the canvas widgets in cairo surfaces, but it will still use CPU blitting when it actually copies the image back to the window.
I couldn't find the second option, even grepping for it in git master.
Edit > Preferences > Appearance > [ ] Possibly Improve Slow Graphics Performance
We will not be moving to a new version of GDK at any time in the foreseeable future.