Re: are battery saver apps really work ?
No.
The only one that works is Greenify, since it actually forces apps to shut down until you start them back up again.
This is unlike other battery saving apps, which only automate what people have been doing for years to save on battery juice, like turning off Wi-Fi and mobile data when not in use.
I tested GO Power Master, and it actually drained more battery than it saved, and it never actually saved battery power, as all it did was turning off Wi-Fi and other stuff after a certain period of time, which was actually counter-productive since it turned them off when I needed them most sometimes.
Wakelocks aside, Android can already manage battery usage just fine on it's own.