The NSP extension represents the digital eShop version of the game. Unlike XCI files (cartridge dumps), NSP files are designed for direct installation to the console's NAND or SD card.
An Analysis of the "Miitopia Switch NSP UPDATE" Ecosystem: Distribution, Functionality, and Preservation Implications Miitopia Switch NSP UPDATE
The game's world is also worth exploring. Miitopia's vibrant environments are full of secrets and hidden areas, encouraging players to explore and discover new things. The NSP extension represents the digital eShop version