The larger screen is a nice upgrade! Oof, looking at the videos however, they're still making some baffling staging decisions that are breaking the illusion. The giant spotlights behind the screen really highlight the edges, I wonder why they didn't use the common tactic of adding some decorations to conceal the border? Or just avoid lighting the back of the stage.
Some synced background elements in the video so the Vocaloids aren't dancing in a black void could make all the difference too. With Vtubers and other virtual performers using LED screens in concerts very effectively, I think Miku Expo would benefit from borrowing some of the techniques that have been developed.