Because the Switch version is already a heavily downgraded port of a PC/PS4 game, emulating the Switch version on a PC is generally inefficient. If you have a gaming PC capable of running a Switch emulator, you will get a vastly superior experience—with higher resolutions, better textures, and 60+ FPS—by simply playing the native PC version of Batman: Arkham Knight via Steam or the Epic Games Store.
The phrase "free download" in the context of "Batman Arkham Knight Switch NSP" raises concerns about piracy. Video game piracy has been a longstanding issue in the gaming industry, affecting developers, publishers, and console manufacturers. Piracy not only leads to financial losses but also impacts the ability to support and update games.