Olympus Viewer vs IB
Yes, the beauty of Olympus Viewer 2 is that it is the camera's jpeg engine, extracted to use on your computer. So you shoot RAW, then load the picture into OV2. Now you can change almost any of the camera's settings except the exposure and focus related ones and process into the jpeg that would have come out of the camera if you had the settings that way.
You can fix the white balance easily. You can add any art filter/try different ones (even if your camera doesn't have that art filter!).
And for the XZ-1 the most important is to turn the noise filter from Standard down to Low.