So here is an .aep file (from CC 2014, but I also have CC 2019). The layout is just a rough sketch at this point and I’ve attached thumbnails of the clips in lieu of the full-sized files, but the general idea is just having each clip start to play when its border reaches the comp boundaries. I’m thinking that the point at which the clip comes on screen will be determined by a null parent layer that controls the speed of the animation as I’ve done here, but I’ve also thought of arranging the whole thing in a precomp.
The first frame of each clip should be just the actual first frame, unless I’m misunderstanding the question.
I’ve also attached a thumbnail preview of the (very) rough sketch of the entire list of clips that will be scrolled through.
https://www.dropbox.com/s/i6lvsjz4r7baea7/cow-videos-and-aep.zip
Thanks!