If you’re just using DHCP, you won’t. What Netplan does is take a YAML input file and renders it as a systemd-networkd or NetworkManager configuration file. It’s a very quick and easy way to configure your network, and even have a try command that auto reverts in case you get kicked out of your SSH session.
It seems like what they’re doing for the desktop is hacking up NetworkManager so that it saves back its config as Netplan configs instead of regular NetworkManager configs. That’s the part I’m confused about, because NetworkManager is huge and Netplan doesn’t support close to every option. Their featuresets are wildly different. And last time I checked, the NetworkManager renderer was the least polished one, with the systemd-networkd one being close to a 1:1 match and more reliable.
It made a lot more sense when it was one way only. Two way sounds like an absolute mess.