Basically android General User interface is made of multiple apk files .. Apps in other words.
System/framework/framework-res.apk contains the android design that apps would use it. And how phone looks in general
Systemui.apk is status bar and the pull down and pop ups
Those are the very main ones.
You should edit the apk files and swap the touchwiz images with the one you want..
For other system apps, you would want to edit them too separately (settings, camera, music, etc.)
I don't know much about it .. But that's all I can help with.
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