Sorry about that! The native Preview application does more than text
but not video. ~ Mirroring video from YouTube (google) may require a
search of some depth; especially with a newer M1 Apple. While some
things just work, finally in Big Sur, that may still be unconventional.
YouTube has options to run differently in iOS for iPad or iOS iPhone.
For larger coverage of most things YouTube best look via Google, for
their interest in proprietary evolution there, would be more in focus.
There is/was feature to enable 'picture-in-picture' with YouTube in Mac..
What worked within Intel-based Mac, maybe not-so-fast in Apple Silicon.
• How to enable picture-in-picture for YouTube on your Mac | theverge (update 2020)
https://www.theverge.com/2019/12/27/21039447/pip-picture-in-picture-mac-safari-youtube
Integrated-applications within Big Sur may have several features I've
not encountered. Since my Macs range in their OS from "pre-OS X"
'Mac OS8' through macOS 10.14.6. Or across several build decades.
Several valid ideas may be forthcoming.
..Sorry to waste our time here..
Good luck & happy trails!
🌞🌿⛵️🎣🌻🐢⛄️🌤🌎