Task managers,mobile cleaners and the like....? topic

I would like to know what your thoughts are on usage of these apps, do they work?

I have personally used,

Greenify
Es task manager
Du battery saver and there cleaner app

But I have read they use more ram then they free up etc..

Also xcore, and core2 management. (these shut down one core on dual core devices) Do these save battery or not? Surely since these phones are generally optimized for dual core processors, closing one causes the remaining core to work twice as hard and wont save any?

Are any if these applications worth having?
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