Before wrapping my RKEP Ultimate Grip I usually take the plastic and wrap it on top of the original grip so when I remove it in the future, it won't leave a sticky residue mess. And yes I may be different by wrapping a replacement grip on top of the original grip, but hey it's all down to personal preference. I used to use regular overgrips, but that caused blisters :/
Since a replacement is obviously thicker, and I wrap it on top of the original grip, would this affect the overall weight/balance of the racket?
It's not really easy to remove. When I did it, some part stayed on and I couldn't remove it completely... but for me it's ok, as you don't really feel it, when you're done with wrapping.
Moreover, I noticed that my headlight racket felt more "headheavy" than before (with the original and the additional grip)...