Hi!
It would be good if you'd explain a bit more about what you want to achieve...
But to your questions: you can add a texture to the light by creating the geometry yourself and assigning the Corona Light material to it. This is what Corona Light does internally after all.
As for the intensity of the light, of course the texture gets blown! Try looking into a real-life strong light... You can adjust the exposure to see more of the texture, but then the image will be darker of course.