I think this was most likely done with something like C4D's MoGraph deformers to create a jumble of shapes changing scale, position and colour using an Random effect.
Arranging them into the letter's space is a little trickier. You can use the Text spline primitive to create the text and an Extrude emitter to give it solidity.
Finally, you can place both the mograph objects and the Text object into a Bool, setting the option for Intersect.
There'd be a lot of manual placing and keyframe animation (I think), but you can achieve all that with AE's included C4D Lite, just not directly in AE itself.