Still, as I mentioned at the beginning, many euphyllid species can touch each other without issue. Oddly enough, specimens of E. ancora, E. paraancora, E. divisa, and E. paradivisa can be arranged so that they not only touch at times, but have their tentacles intermeshed with each other's. So, it's possible to create a very beautiful and unique setting in an aquarium if different species with different looks are placed together. Trying to do so with the other species is very risky, though. While a few hobbyists have successfully mixed specimens of E. glabrescens in with these others, this almost always ends badly. I don't know of any cases of the remaining species being placed with those above either, and found nothing online suggesting it has been accomplished successfully. So, I wouldn't try it unless you're willing to take big chance and keep a very close watch for any troubles.
Torch should be the most aggressive I'm the family.. but two frogs will even attack each other. I personally have a frog and a gold torch that could touch if they wanted to (they probably do in the middle of the day) and not having any problems. I've never seen them attack each other or show any signs of stinging.. I will likely move the torch father away (again) just for my own comfort...