I could be wrong, but the best I can figure is they are the same, or the Uniflow II is an evolution of the Uniflow.
It looks like RCBS has dropped the "II" moniker though as it is not listed on their web site.
It looks like the Uniflow and it's current variants are a modular system, at least the standard and the competition models. I am not sure about the Quick Change model.
You can buy the pieces that make the competition model the competition model and fit them to the standard Uniflow.