The only unique (I think?) thing about phone link is that it enables you to use your Android phone camera as a webcam, which can be handy if you don't have a quality webcam. I think its only in the beta version though.
I'm not sure if this is a Pixel feature or if its available across all of Android, but there is an option when you connect over USB to connect your phone as a webcam - but that is of course tethered instead of being wireless.
With phone link I have tested the beta version and you can use your phone camera wirelessly after initial setup. At least I was able to do this using a Redmi Note 9s without any obvious issues, apart from the privacy concerns noted elsewhere.