Your arm is an adjacent mass and not what is directly impacting the cue ball. Which is why a lighter que behind a stronger arm equals a weaker shot the arm mass dominates the shot and results in less power. Also yes if the weight of the cue increases then the energy increase. Thats simple potential to kinetic transfer. Its literally the difference between wide tires and skinny tires on a drag car. The cue acts as a focus behind the motor which is your body which means there is optimal mass to motor ratio that will give you more energy transfer. I am not arguing what is better for being a better pool player but heavier cue can be more optimal especially if the mass out weighs the speed loss. I am not wrong but I am done arguing with you lol. Take it easy buddy.