Actually that's odd and I need to look at this, but I don't think that is actually working. OpenGl and Metal shouldn't be able to work together. Either the renderer gets set to Opengl when output Openglnb is chosen or the output is set to the default when renderer Metal is chosen.

All I can add is that benchmark results are essentially identical when using any combination of renderer=opengl/metal/auto with output=opengl/openglnb.

I did not try texture and surface as they do not provide scaled output. Texture also black screens when used with metal (however when you type you can see the characters briefly show up and then disappear when you let go of the key).