As a general rule only corals of the same species can touch, and even then it's not a sure thing. . . I am sure there are exceptions, in-fact certain euphyllia are known to cohabitate well, though not uniformly across the genus or even amongst different localities (collection/origin locality.) Your best bet is to give all your corals enough space and or diligently research them to see which ones can safely cohabitate (keep in mind this is excluding the fact that corals can grow over the top of each other and shade each other out separate of any actual stinging/warfare.)
Probably worth noting a lot of the info you find will be anecdotal (much like the "evidence" I used to inform my above post ^^^ haha)