Good luck if you plug in an external monitor. (Not to speak of refresh rates)
I don't know about that; I use just one screen (laptop or HDMI, not both at the same time which is presumably what you're referring to) and it works for that. That's not really what the previous person was talking about either.
At the office I plug in a monitor over USB-C and that just works on my X11 laptop. If something in a browser on the monitor was too large or too small I'd just zoom in/out until it was fine.