I don't have a balloon clarkii but my normal clarkii is not a nice little fishie... And I don't think the bite of a balloon will be any weaker than that of a normal specimen.
But I have a pair of balloon black ocellaris, and they act just like the normal-bodied ones, including the fancy pair that they share the tank with. The main difference is the funkier swimming mode, but everything else is unchanged.
A few pics attached. :thumbsup:
Best regards.
Daniel.