Well, there is always the AOSP side of the story if you want a pure kitkat like experience. You will however, lose all spen functionality. And as well, you will be knoxed. Flashing roms requires root etc (unless you already are rooted)
As for the app icons, maybe there are some leaked s5 apps you can install for the look and feel of that?
Sent from my SM-N9005 beast of a phone.