For the Nintendo switch.
If you remove the wifi you will not be able to update the console firmware.
However that should not be a real problem, I don't recall a firmware update that was required to keep using the console.
If you have a dockable version like the standard or OLED you can connect the dock to ethernet when needed.
Many games have additional DLC that would require a connection, such as Mario Kart which has a paid DLC for added tracks, but these are not required
Most game cartridges should work straight out of the box, however there are some larger games that do need a download to work.
Seems like sports games like NBA 2k and MLB the show typically need downloads as well as some other large games.
There have been occasional stories of games shipped with a glitch that needed an update to be playable but that is rare.
Typically you should be safe with all first party games, and a quick google of the game title should tell you if it requires a download to work
