MacOS Big Sur - Screen Rotation
 

I configured 3 external monitors with 2017 Macbook Pro 13.
2 of monitors are in portrait mode (90' rotated)
Everything works fine but I noticed that portrait monitors are little laggy.
When I set them back to landscape mode they work just fine.
What I noticed are that when a monitor is set to portrait mode, system detects as 27.5" monitor because of its resolution of (1050 x 1680).
I think because of its height 1680
I hope this helps for improvement of software for MacOS in the future.
Thank you