The quality of the render does not affect the file size. As to the questions of JPG quality. A JPg can look just as good as a bitmap(to the naked eye. It all depends on the range of colors in the image and the subtle gradations of each. If you have an image where you don't need to capture suble gradations a jpg will be great. I should say that most images do not need the full quality of a bitmap to look just fine. Experiment and see.