I have a bunch that are touching, (zoa's and palys)
As far as multiplying faster I think it depends on your tank and the palys or zoa's, you really can't group all zoa's and all palys into the same catagory when talking about fast growth.
Some zoa's grow fast, and so palys grow fast. It just depends.
What may thrive and multiply in your tank, may not thrive and multiply in my tank