How do I play choppers

i believe choppers when they play against loopers, they mix up their chops between heavy backspin, and very light to no backspin, even dead balls, when we try to loop these light/no spin chops that is where we go past the table every time. i think adjusting your loop to a loop-drive and still brushing the ball lightly helps keep most balls on the table. my rule of thumb is loopdrive if you are not sure how much backspin is on it, and vertically slow-loop the ones which you can tell have heavy backspin by the flight of the ball.

what if the player have on one side a chop and on the other a normal rubber(bryce)??? he chops first ball and attacks other one 

This does put a bit more pressure on you to play a good topspin.  If yo are pushing then try to make sure you find his pimples side so that it is more difficult for him to attack.

yes i understand that. for me its hard to attack against chop. so i must take cre of my defending side. right? does any exercises exist which can help me to have better defense??