I've bought a second Switch and when I did, I moved a second player from my main island there. It worked out nicely
The transfered player does get to keep all their apps, including terraforming. So you'll have it from the start. No need to get 3-Star town first.
Some of the town related achievements get reset.
While picking a good starting map on the second Switch, you can close and restart the game without messing up the transfer. So don't feel like you're stuck with the first 4 map choices.