It makes a number of changes to the opening sequence, and even to the broader game, to make the opening less clumsy: Skyrim Special Edition mod Opening Scene Overhaul SE by PublickGamer changes that.
Another is that you come face to face with Ulfric, one of the most important characters in Skyrim, and the game never acknowledges that ever again. One of these is the way the Imperials are several seconds behind events - it feels like their dialogue during the dragon's appearance ought to happen well in advance of its actual play time, making them sound ridiculous. Oh, I don't mind the whole rounded-up-for-random-execution thing, and Alduin turning up right before the axe drops is rad, but there are some things about it that really, really bug me. Skyrim is great but it doesn't open in spectacular fashion. Skyrim: Special Edition is the gift that keeps on giving.
