If you're running macOS Mojave or later, you can use QuickRes to quickly change your display resolution. Here's how:
Open System Preferences and click Displays. Click the Scaled option. Select the resolution you want to use from the list of options.
You can also add a keyboard shortcut to quickly change your display resolution. To do this, open System Preferences and click Keyboard. Click Shortcuts, then select App Shortcuts from the sidebar. Click the + button to add a new shortcut. In the Application field, type QuickRes (no need to include the path). In the Menu Title field, type Change Resolution (or whatever you want the shortcut to be called). Finally, click in the Keyboard Shortcut field and press the keys you want to use for the shortcut (we recommend using Option+Command+R).