First of all go to the security App
Then go to the battery section which is shown👇
Then go to Low Power mode and enable it .
After enabling you will see that your battery percentage meter color changes to yellow
which means that you have enabled the battery saver option and in that you also get a option to Turn off the data while the device is at sleep which will also save battery but on the other hand you will be lacking behind of the notifications of your social media .
P.S I am using Meizu m3 note with Flyme 6 stable Chinese ROM version and the battery works fine with the battery saver option and there is no lag and no slow down in system animations.