The Nintendo eShop digital version of Pillars of Eternity: Complete Edition, including all bug fixes and improvements, requires 29 GB of available storage.  Because this exceeds the available internal storage on the console, the eShop version of the game must be installed to a microSD card (sold separately) that is inserted prior beginning the download.

Any microSD card used for game storage must have a read speed of at least 60 MB/sec.

For details see the Nintendo microSD Card FAQ:
https://en-americas-support.nintendo.com/app/answers/detail/a_id/22481/