if the videos are at the same lengths when i faced similar task on a much worse hardware i baked a grid of lot’s of videos into fewer higher resolution videos with after effects and placed them on quads with texture transforms so individual quads were addressing different parts of the same baked video. that saved much performance however it is the best when all the videos are more or less have the same length. also you might want to write a little metadata file which video is positioned in which video-grid and where on that grid.
if only the set of videos have the same length which you want to switch, you might use baking on them on their individual video-grid so you end up with 80 baked videos with a little metadata so texture transforms know where to look. if none of the videos have the same length then you have to tolerate or account for the framerate-drop when switching between them