I'd pick 'Follow system settings' as it allows users to stick with their preferred mode and reduces unnecessary battery drain on OLED screens.

I'd pick 'Follow system settings' - users should have control over their preferred mode, and forcing one might not work for all demographics or environments.

I'd pick 'Follow system settings' - users should have control over their preferred mode based on their device settings.

I'd pick 'Follow system settings' - users should be able to choose their preferred mode based on their device settings, seems most user-friendly

I'd pick 'Follow system settings' - users often have a system-wide preference and forcing an app's theme can be jarring when it clashes with their OS settings.