I am on an Alienware M16 r2 laptop with an Nvidia dgpu and an Intel igpu. When using an external monitor, I plug the displayport into the USB c that's wired straight to the Nvidia gpu. This causes some horrible lag on the desktop and games because the igpu seems to render everything and then send it over to the dgpu. This problem disappears if I disable the igpu but I need it for battery life when at school. Windows doesn't have this issue and can automatically switch gpus with the mux switch when there is no external monitor.