If a website offers a direct descargar button for Switch games, it is almost certainly a piracy site.
Websites that cater to this search typically offer bundles or "repacks" where the emulator, keys, firmware, and game updates are pre-configured to work instantly. descargar roms bios para emulador de nintendo switch upd
Nintendo's official stance is that downloading keys or ROMs from the internet violates copyright and the DMCA. The only legally defensible way to obtain these files is by "dumping" them from your own hardware: Switch Emulator Suyu Setup Guide If a website offers a direct descargar button