Those court cases were overridden by Congress... when they passed the DMCA.
Under the DMCA, IT IS A CRIME to:
1) circumvent an "effective" copyright measure for any purpose, except specific, delineated purposes and cases which must be approved and reapproved by the Librarian of Congress every 3 years;
2) traffic in the means or technology to so circumvent a copy protection measure, with no exceptions.
The definition of "effective" is so weak that it applies to anything, even a bit of JavaScript that intercepts right click so you can't "Save Image As". It basically means, would the copy protection measure prevent copying "during the normal course of its operation". I.e., if it's buggy, employs weak crypto, or is otherwise trivially defeated, too bad. You can still catch federal time for breaking it.
In order for a Switch emulator to work properly, the copy protection on the game must be defeated. So even if you dump it yourself and a court somehow rules that copy to be fair use, YOU ARE STILL COMMITTING A CRIME by the very act of dumping it. Therefore, it is illegal to run a Switch emulator to play legitimate Switch games, irrespective of whether those games are "legal" copies or not. And a court may rule that Switch emulators are illegal to distribute as well, since they only have illegal uses.
I am not a lawyer, so I recommend you find yourself a good one if you want to mess around with Switch emulation. Best bet is to not get involved with it at all. Forget about preservation. The Switch and its games are not yours to preserve.