In my experience as long as you provide enough hiding places juvies do fine together. Space is important as well (10 gal for 2 juvies is enough)
When they are too close together and cant avoid one another I have seen some nipping. But given space and hiding spots all will take a corner and be done with it.
The trouble comes when sexual maturity begins (not unlike humans lol) Once that happens males need be separated before they duke it out. And females need be separated from the males until they reach a large enough size.Youve got several months at least before this is a concern.
I have noticed the favorite thing for cresteds to do is watch each other..I use screen cages and have my cages in order of size so nobodies staring at anyone a great deal bigger or smaller. (just in case thats a stress)
I haven't decided if they watch each other out of curiosity or watch to make sure their territory doesn't get violated.