I really dont know how to determine a fish has an outgoing personality. For the most part, they just swim around and mind their own business without much interaction with other fish. My achilles will occasionally have a squeamish with my personifer angelfish and with the pbt. Nothing serious though. I have a 4.5" blue hippo too that they dont ever even look at or interact with.
Some people have problems with the achilles and some with the pbt without even keeping the fish together. I guess it is a really hit and miss. I think if kept separately, the chances of success is pretty good. They are fairly hardy if you can keep your tank ich free.