Years ago I watched a documentary about the Findhorn commune. All their decisions were supposed to be communal. It was full of hippie types who didn't want to impose their decisions on others or take responsibility, and would talk and talk without deciding anything. At the end of the day everything ended up being decided in practice by this one decisive woman. She never presented what she was doing in this way, so everybody got to pretend/not realize that she was really their boss.The fact that they're anarcho-communists suggests that a large degree of centralised organisation is not the likeliest of options.
Just because Antifa claim to be/believe themselves to be/mostly are anarcho-communists doesn't mean that in practice a relatively small number of people aren't making the important decisions. Who knows? Not us. Presumably the FBI have a pretty good idea.