In my country workplace regulations forbid working on laptop screen anyway - if a worker is supposed to work on computer for more than, iirc, 4 hours a day, the

In my country workplace regulations forbid working on laptop screen anyway - if a worker is supposed to work on computer for more than, iirc, 4 hours a day, then external screen is mandatory. And it's not really about a screen size, it's more that you are not supposed to be looking down, so the external screen top border must be at the same height as your eyes.