Both Starks ideally. All the clues point to the World B one, but I can't get over the World A one lying about this, and maybe the clues are more oblique than that.
And I think this is a guy based on the radio intercept during Bucky's show. But if the rest of the HYDRA based intel is a red herring, and the purple sock is more a joke about Zemo's costuming, it wouldn't have to be.
There were five disappearances, we should be able to detain more than two people.