Migration isn’t as smooth as it should be. Generally it’s good at transferring Google accounts, messages and phone logs, reinstalling apps, etc. But it doesn’t automatically log you back in to everything, so there’s usually a period where you keep opening an app for the first time since the move and have to set some things up (although I heard that was changing?). No idea about the home screen layout, as I use Lawnchair, and most custom launchers have options to save and back up layouts. But it wouldn’t surprise me if it didn’t…
I’ve recently started using IP Webcam to turn an old handset into a camera. It’s not open source, but it doesn’t seem to be too annoying, and so far it seems to work surprisingly smoothly and has been up & stable for a couple of weeks.