First, let's clarify what "NSPJP" means. An NSP is the digital file format used for Nintendo Switch games and DLC. The "JP" suffix indicates the Japanese region release. While the core games are identical across regions, the emulator wrapper and ROM revisions differ significantly.
The Nintendo Switch is region-free, so a separate subscription is not needed to access this content. Here's how to download the Japanese N64 app: nintendo 64 nintendo switch online nspjp better
Since the launch of the N64 app, Nintendo has released several patches to improve the experience. First, let's clarify what "NSPJP" means