form is the primary factor for tennis elbow as you will mis-use arm force to hit the ball.
you should use body/should turn to hit the ball. loss wrist. if you don't use 'arm force', u shouldn't have any tennis elbow.
i don't think heavy racket contribute tennis elbow, but i do think it help to reduce the chance of tennis elbow. heavy/small head racket usually required 'full swing' in good form otherwise ball cannot pass to the court.