I honestly haven't got a clue right now either. Just seems to be factions split among the Titans. Bigfoot Titan sorta confirms that as he wasn't aware of the 3D gear.
It seems Annie, Reiner, and the other guy's objective is get Eren for some purpose. His dad may even be in on this conspiracy. Also it seems Reiner had to choice but to reveal himself because of his broken arm started to heal. Evidence was when he took it off and the Titan vapor appeared. The other guy as the main Titan that started all this in motion threw me off.