You can designate primary and secondary consoles. The primary console has access to everything. The secondary consoles has access to anything as long as it has an internet connection, and the primary console isn’t using downloaded content. I can’t tell if it means the same game, or if using any downloaded game on the primary console means the secondary consoles gets booted. Also, on the non-primary, only the “owner” of the game can play the game.
I think you might be able to finagle some stuff with playing the primary in offline mode and using the owners account on the secondary, but to me it mostly ready as: buy cartridges if you might use multiple switches.