Set this to 1x (720p/1080p) . Downscaling to 0.75x can provide a massive speed boost on midrange phones if the option is available.
Though an official app does not exist, the open-source community has experimented with the code: Source Code Experiments decaf emulator android
Development on Decaf has slowed significantly in recent years. The lead developer, exjam, noted in late 2020 that personal life changes (like starting a family) had reduced the time they could dedicate to the project. While it still receives occasional updates on GitHub , it is largely considered an experimental project rather than a daily-driver for gaming. Set this to 1x (720p/1080p)