After I typed some answer here, then went off and did a test, I see again, I should render before I speak.
Although the Glow radius and intensity is in the Chor properties, we can get some measure of control by adjusting the Ambiance Intensity of any Group using Glow, but this seems to control how much of the object is affected by the Glow, not the same effect as the Chor's Radius or Intensity.
If you are using the Diffuse Color only, then the brightness of the color seems to have some affect on the Glow Amount, but again, this seems to be a control over how much of the object has glow, and not the radius or intensity. Here's a picture of my test, this is one Model containing four spheres, each one has it's own Group.