What does "Mirror my video" do?
By default, a reversed image of yourself is displayed when you share your camera. To view yourself how others in the meeting view you, you can disable the Mirror my video setting. This does not impact how other participants view you, it only impacts your view of your video.
This is helpful if you are presenting something in the background (like a whiteboard) or your virtual background includes text. Disabling the Mirror my video setting allows you to view the text the way others do.