As far as I know, the 'cache' can be safely removed from apps to create more storage. If an app needs the stuff you delete, it will create it again next time you open it. 'Data' is different. Don't delete the Data in Contacts Storage or you will lose all your phone contacts!
EDIT: use Astro file manager. In settings there's an option to clear cache data from all apps and it only removes stuff that can be removed safely.