I grew up playing with an Eastern forehand. My normal stroke has plenty of topspin, but, when I want, I can add some super-excessive topspin by hitting through the ball with more low-to-high follow-through.
The grip does not dictate the amount of spin- it is the speed and direction of the racket as you strike through the ball.
Having said that, the grip does tend to dictate what might be called your "normal" path through the ball-- but, I have seen McEnroe (Continental) hit with lots of topspin and Nadal (Western) hit pretty flat shots.
My suggestion is to use whatever grip you like best-- and then learn to be a flexible and well rounded player who can create a wide variety of shots as required by the situation.