I'm glad you noticed the two birds at the end! Birds, wings, and cages are such important motifs in this series.

This episode was already a bit longer than the normal ones, so I think they had to cut some lines from the manga, but the speech between Erwin and Levi was more like this: Erwin: Who was it that killed my subordinates, killed your friends? Was it me? Or was it you? Even if you had gone together with them to ambush me, do you really think they would have survived unharmed? Levi: (If I hadn't left them behind back then.....) You’re right…My arrogance…my own shitty fucking pride… Erwin: "YOU'RE WRONG! IT'S THE TITANS! Where did the Titans come from? Why do they exist? Why do they devour humans? I don't have the answers. None of us do. Limited by our ignorance, we'll continue to be devoured by the Titans. If we just stay shut behind the walls, we are never going to escape this nightmare. Take a good look around you! No matter how far you go, there aren't any walls here. In this wide open space... I believe there is something there, illuminating our despair. But there are those who seek to prevent us from venturing beyond the walls. They are consumed by selfish thoughts of their own losses and gains from behind the walls where it's safe! It's only natural. During the past 100 years, hindered by the walls, the eyes of humanity have been clouded. They cannot see the landscape that lies on the other side. But what about you, Levi? Will you let your eyes remain clouded? Will you kill me and return to the darkness of the underground? We will not give up our journey outside the wall. So fight for the survey corps, Levi! Humanity needs your strength!"