Only external display very sluggish

My laptop screen is 3840x2160@60Hz and my external monitor is 5120x2160@50Hz.
It works smoothly like only using laptop screen without connecting external monitor if I choose Extend to the right display.
After changing to Only External monitor display and close laptop screen(it becomes black) in display setting, it’s very sluggish that I need to wait for typing. Changing resolution of external monitor to 3440x1440@72Hz in display settings doesn’t help. It seems like Qubes OS is still consuming resource for closed laptop screen. Is there anyway to detect this?

I have already increased RAM in dom0

qvm-features dom0 gui-videoram-min 166400

My current solution is to move external monitor to the left of laptop in Display - Advanced then it automatically becomes Mirror Displays, the mirror source is external monitor 5120x2160@50Hz. Then reduce laptop brightness to 0.
It is not only Qubes OS related problem which can also seen in Windows and Ubuntu after searching. But other system may install GPU driver to solve the problem which isn’t practical in Qubes OS now.

I need to run xrandr --output eDP-1 --auto to let Qubes OS recognize 5120 instead of built-in monitor 3840x2160.

It’s an xorg issue DisplayLink displays runs at 1FPS when laptop lid is closed.