I plan this summer to buy another Nintendo Switch so I can play on the bus (And my SO can play at work too)
But my profile is already on the Nintendo Switch I have; Can I transfer it to another Nintendo Switch?
At this time you can transfer a Nintendo Account between consoles by deactivating the first and then setting the new console as the active one. Digital purchases can only be played on the active console for a given account so you and your SO will not be able to share a single digital purchase. Most importantly your saved games will NOT transfer — saves on SD cards are encrypted by unique hardware not account.
More information on Nintendo's Support site: How to Transfer Digital Games Between Nintendo Switch Consoles.
That said, Nintendo has made many promises about their upcoming Online Services, including theories and hints at the possibility of saved game syncing. The optimists are hoping for something like Sony's PlayStation Plus subscription service, for both save and purchase syncing between multiple pieces of hardware, though that might be too much to hope for.