Whats with different bore sizes? What is the difference in tone with each bore size? And whats weights (example: Light-weight body and medium weight bell) How do those things effect the tone?

The heavier the body of the instrument the thicker the skin and the deeper the tone. A larger bore size has the effect of giving a broader richer tone and makes low note easier and uses more air so long passages need big lungs where as a small bore makes it easier to reach those high notes but blow too hard and it will have the effect of stopping the instument.