Even with switch res x, the most I can push vertically is 1080 with the same aspect ratio. I have pushed a standard 16:9 4K before.

In particular, my MacBook is the 2015 model, 15 inch.

My solution is switch res x with two outputs, 2K each, and picture by picture mode. However it has problems. Like you can’t zoom cast a window that overlaps the center.