Indeed. There isn't really anything anyone can do to stop them, I suspect. It's clear they have no care for anyone on their side (the first one killed some Skulls for fun), so they're a pretty risky weapon. Still, we haven't seen this one be a total moron and go after its comrades... I guess Allen and Kanda are putting up a better fight than we think. Then again, in the next chapter... It's hard to tell just how different this one is. It could be more evolved than the last one, at any rate. Somehow.
Same here, this Level 4 Akuma seem to be pretty much the same as the other one, as in he despicably EVOL, more so than other lower level Akuma since they peaked the evolution pack for an Akuma and have free card to do whatever they please, they´re pretty much the Noah´s second in commands, plus with those human-like expressions, you can see their sadistic expressions more easily than with a freaky demon/animal looking thing.