Side Effect After Composite Veneer Treatment?

Without seeing the teeth, it is impossible to really know.  It is possible (likely) that the teeth were altered to some degree to put the composite on.  Removing the composite will require that they be ground off and can scar the enamel.  This CAN be polished, but may never return to how they were before.

 

It is best to plan to have porcelain veneers done and hope that the composite can come off.  This situation is very common, as composite veneers are rarely satisfactory.

Most veneers whether chair side with composite or porcelain lab made ones are rarely reversible.. The surface of  teeth  underneath the veneer always have to be altered at least on the enamel layer and etched. So , should you remove what you have you'll need replacement of some sort. 

You mentioned thicker teeth, well that is exactly why the teeth need to be roughened, enamel somewhat removed so that teeth do not get bulky and uncomfortable.

Yours probably has not been cut off too much( since you say they are bulky)  but for sure had to have been etched, and even if they are able to remove the composite veneer and polish them, they will never be the same and they may be very sensitive. 

This is very common as almost always chair-side composite veneers do not come even close to the real porcelain ones.