Using custom game configs
Sometimes, you may find that you want to use different settings for different games.
PPSSPP has support for this, although the UI is admittedly not very good. Concrete ideas for improvement are welcome.
Anyway, here's how to do it:
In-game, pause and click "Create game config". Then go into settings (without exiting the game) and configure things the way you want them. Exiting out to the main menu, you'll find that the changes only applied to that game.
When a game has a custom configuration like this, its icon will be overlaid with an additional little gear icon in the Games and Recent browsing tabs.
To delete a game config and use the "global" configuration for the game again, pause the game and click "Delete game config".