When I set my external monitor as the only active display, the desktop environment and all application lag so much, each action takes too long to show up (the mouse movement is responsive though). The CPU/GPU usage is also very high even on idle.
I upgraded both Xorg and amdgpu driver, I’m also using the latest Nvidia driver 530.41.03. Still have the same issue, the external monitor is barely responsive.
Edit: I downgraded to 525.105.17 and everything works perfectly.