I wouldn't risk it with anything expensive unless you have spares. Some people have no issues, but there are also plenty of people to vouch for the fact that it can end badly. I think water column size may be a factor. But I played musical tanks with BTAs for a while to get to the bottom of it. In the end I confirmed with certainty that at least in a small tank, certain BTAs will kill each other. After the dust settled, I lost 2 black widows and a green, but the RBTAs fully recovered and never deflate any more now that they are alone. I know for certain the Black widows and RBTAs are a bad combination. However I have a wild type that is purple with green tips that is getting along fine with a white flecked orange one in a 10 gallon tank. I learned my lesson. I think its ok to try it out, but always be ready to move one to another tank. The things to look for are random deflation with the tentacles looking like spaghetti and paralyzed. They will stay like this for a few hours or longer and come back. If it happens enough, it will die. I found this only happens when I mix incompatible BTAs and can continue for some time after they are separated, but eventually subsides if you catch it soon enough. It does not seem to matter if they are touching either.
I think RBTAs are the most hardy ones you can get and the best option for a beginner, but they are also the most aggressive toward others. I'm not sure which ones did in the black widows, but form here on out I will be giving RBTAs and black widows there own tanks. I think having separate tanks is better anyway, because you can have more types of clown pairs.