Why can video playback through Miracast from a laptop slow down when the lid is closed?

Question

Iron

The point is this. There is a laptop with Windows 10, there is a TV with a dongle connected to it, which can do Miracast. I connect to the dongle over the air from a laptop, set the duplication of monitors in the settings, everything works more or less tolerably. The video is not broadcast from a media player, but from a browser from one of the sites that allow you to watch movies and TV shows online. It happens that video artifacts start (running squares), but this is rare and tolerable, better than nothing at the moment. But as soon as I close the lid, or switch the display mode in the settings to only the second monitor (dongle connected to the TV), the brakes begin. Not running squares, namely the loss of frame rate.
Tell me how to be and what to do? I suspect that the problem is that it switches to the second video card. Laptop on AMD, cards like this: AMD Radeon HD 8650G, AMD Radeon HD 8670M.
Clarification: Miracast works directly over the air, that is, it's definitely not a router or some intermediate link, it simply does not exist.