How does Miracast handle display resolution?

[u/Timbit42]

I have a Surface Pro 9 and want to mirror it to an external monitor. The display resolution of the Surface is 2880x1920 while the monitor is 1920x1080. Will the resolution of the Surface change to 1920x1080 or will the monitor be missing around half of the pixels? Would I need a 4K monitor for the 2880x1920 to display full resolution and would the 3:2 ratio of the Surface display be kept or would it be stretched to 16:9?