Miitomo was a mobile-exclusive app (iOS/Android) released by Nintendo in 2016 and shut down in 2018. You cannot download or play an official PC port.

Even though PCs are powerful, mobile apps can sometimes stutter on emulators. According to Techy Indians , many performance issues are self-inflicted and can be fixed with a few tweaks:

Running Miitomo on a desktop offers several advantages over the original mobile experience: