My wife and I would like to share a home island, which is easy enough to do on a single Switch since all players on a console share the same island. What we'd really like to do is play at the same time though, each with our own screen (i.e. not the local multiplayer where everyone is tethered to the primary player). If we get a second Switch and second copy of the game, is there any way to make this happen while still simultaneously allowing both players full access to their property?
If you buy a second Switch, you're no longer sharing the same island. There is no cloud save transfer available for the game. There will be a data recovery service available later, but it doesn't sound like it can be used to keep an island in sync between two Switches.
Each Switch will have its own island. You can use local or online multiplayer to visit the other player's island or have them visit yours to play together on separate screens.