A. agassizii males are pretty territorial. So no to keeping cockatoo's with them in a 29 IMHO. And I'm not sure I would keep the agassizii's in the 29 if it were me either. I had some in a 65 gallon (36"x18") and the male was super territorial in that large of a tank and didn't seem to have enough room and killed every other male agassizii in with him. They might do OK as the only bottom dwelling cichlid in a 4' tank though. So no kribs either IMHO.
If there are other confusing shorthand abbreviations and acronyms used here that confuse you, you can look them up in the beginner's sticky: Forum abbreviations/acronyms.