To change settings for a loaded core or game
Press the menu hotkey (usually F1) to access the Quick Menu while a game is running.
Go to Core Options to adjust settings specific to the loaded core. Common options include internal resolution, aspect ratio, and renderer.
If you want to save these changes for the specific game, go to Quick Menu > Overrides and select Save Game Override to create a unique configuration file for that game.
To save a setting for a specific core, go to Quick Menu > Overrides and select Save Core Overrides.
For a specific game, you can also go to Quick Menu > Options and then scroll to Manage Core Options and select Save Game Configuration