XCI files can often be patched to include the base game, all updates, and DLC (like the Booster Course Pass) in a single file.
If you're looking to play Mario Kart 8 Deluxe on your Switch console, you can purchase the game from the Nintendo eShop or download an XCI file from a reputable source. However, be aware that downloading copyrighted content without owning the game is against Nintendo's terms of service and may result in penalties. mario kart 8 deluxe xci