Its going to be more process crimes.
e.g Don Jnr or Roger Stones saying X when Mueller think Y is the truth, even though Mueller will have no evidence of Russia collusion
We know Stone is getting looked at for mouthing off about Wikileaks. He wasn't even part of the Trump campaign at the time. It is hard to see how Don Jr. would be charged concerning the Trump Tower setup. He has the money to fight it and Mueller would get laughed out of court. It would have to be over something that isn't public.