Officially, when you purchase Sniper Elite 4 from the Nintendo eShop, you receive an encrypted NSP file that is tied to your Nintendo Account. This file is installed directly to your console's internal storage or microSD card. The game's eShop page describes the complete package, noting that the Digital Deluxe Edition includes the full game and Season Pass at a great saving.
— The campaign is fully playable with a friend, and many DLC missions support 1-2 players. Multiplayer supports up to 8 players online.
For those looking to experience everything Sniper Elite 4 has to offer on Switch, there are two recommended approaches:
Menu navigation is streamlined via touchscreen capabilities, and the game features a fully remappable layout tailored for the Nintendo Switch Pro Controller layout. Technical Performance and Optimization
Sniper Elite 4 Switch NSP Update: Unlocking Exclusive DLC and Enhanced Gameplay