Reinstall the games you have issues with.
In mobile manager, press clean memory, after this you can set up super clean. Enable as many apps as possible for super clean (notifications from the apps you enable will be affected). Now, every time you press "clear all" in recent apps overview, it will force close those apps.
Don't clear your apps right before you enter a game (wait at least 30 seconds) since some apps like to auto-restart which will cause a temporary CPU workload.