Different SPS species will battle chemically with each other. The more dominant one will win and the lesser one will recede to a point where they aren't touching. Normally, it'll end there, however, it can end in the lesser coral being killed.
I am ordering some frags (around 25) and If I just put them in the tank where I think they will grow well and look good should I ever have to move them or should they naturally grow where they aren't touching or where they are touching but it doesn't bother them?