Oh my GOD! Man you are a genious! I never heard about that Samsungs DVFS before until you mentioned it in your post. I looked it up and thought "yeah that thing needs to go away!"
So I just rooted my phone, installed wanam Xposed and Samsung DVFS Disabler and voila!
No lags in any game, I can even play Spider Man 2 on max graphic settings without any issue! It was barely working on low setting before OH MY GOD!
Before, San Andreas started lagging after playing 10 minutes, now its always smooth, and now I can play all my games with my sixaxis!
An all those customization options in Xposed oh my god i'm just so excited right now
Thanks for showing me the right way man, root is the best thing that can happen to any Android device.
Quick question: What do you use to back up before flashing another ROM? I have been using an HTC device before and 4ext was the way to backup, but I'm new to Samsung scene and I don't think 4ext is compatible with this phone