You'll need to play with the parameters to get the desired look. Some noise is, to me, a nice look- otherwise your output will look too clean. All the filmmakers now shooting digital, whether on Alexa, RED, etc; they all add some noise in post. I own a RED EPIC; The camera has such a low noise floor; that without adding some it looks a little flat, plasticesque.
A better way of looking at it is consider the noise you add "fine grain". Use monochromatic. Not color. Use Uniform, not gaussian. You will need to adjust the % of noise added, based on your frame size. 5k needs a tad more than 1080p. But usually 2-3% will take care of most gradient problems, not be distracting in any way, and lastly; will give your output a bit more "life".
Finally, your output workflow is a whole other issue, but noise shouldn't drastically change the overall quality when added at such a low threshold. If you added 50%; yes your compression would be horrible because of the h264 encoding process and how it uses frames past and prior to build the current frame. But at 2-3%; you are not losing much, and certainly not losing what to the naked eye anyone would notice.