Use emacs to configure xrandr.
(use-package emacs-xrandr
:straight (:host github :repo "zhenhua-wang/emacs-xrandr"))
Simply call xrandr interactively, you would be prompted to choose from a list of supported devices and corresponding resolutions. To turn off the previously enabled screen, simply choose the primary device.
The external screen's default postion is the same as the primary screen (mirror). To change this, run xrandr-set-position interactively and rerun xrandr.