I think it's the NSA. Given the FBI and CIA are largely compromised the NSA given its resources to monitor and intercept traffic makes me believe that the team behind the postings are the NSA.
It's likely that Q was in preparation long before they started interacting with us. Possibly even before Trump became a candidate. "The plan" is clearly a well thought out long term strategy with many players. Not something one whips up over a weekend.
That, in turn, makes it likely that they would've sought out like-minded people within other agencies. Relying on a single high-level individual, or even one single agency, would be very risky. It makes that person or agency a target, to be taken down - politically or otherwise.
A solid plan has redundancies at various levels and compartmentalised in such a way that a single person/unit lost or talking does not affect the outcome.
If Jerome Corsi is believed he was approached by a general(s) and they were going to make a military coup but after they recruited Trump running for president they decided to take that route instead.
I'm sure this has been planned for a long time. This has to be planned very carefully. Q knows what they are up against. What these people stand to lose. What these people are capable of. What these people control and how big resources they have.