How do I know which games on an iOS device save or backup to iCloud?

I'm trying to clean up some old devices, including storage. So I am looking towards deleting some games but I don't want to completely throw away all that time getting to the highest levels. How can I tell what games save to iCloud? Is direct backup to iTunes and my computer the only way to save the data for the ones that don't? How?

thanks so much in advance apple core.