Ullebe1
For the multiplexing, as I mentioned.
A V4L2 camera can only be opened by a single application at a time, but if that application is Pipewire, then Pipewire can allow multiple applications to make use of it simultaneously. Same thing with ALSA, it’s the reason sound servers exist at all, though I suspect you’re already familiar with that.
I also hear that ALSA has some support for multiple applications per device nowadays, though I understand it is much less pleasant to use than a fully featured sound server.
Because Pipewire only handles and understands media streams, so it can stream the output of a window or the whole desktop, but only because the Wayland compositor has already composed the windows and other data it gets from the application to a visual and hands the final result to Pipewire.
Ordinary DNS requests are always plaintext and readable to anyone between you and the DNS server. So regardless of which DNS server you use, your ISP can see all your DNS lookups. For any amount of privacy for DNS, the minimum is something like DNS-over-TLS or DNS-over-HTTPS, the latter of which Firefox uses by default in some countries and supports everywhere.