To the best of my recollection, the only thing the anime really added was some filler involving Adon around ep. 6 or so. This added a little bit more character development for Guts, Casca, and Griffith, but mostly it was just another mission for the Hawks and we get to see another colossal blunder by Adon. Just about everything else that happens in the anime, also happens in the manga and in some cases in less detail. The queen dies the same way in both versions. In fact, in the manga it's revealed that she's romantically involved with Julius, the king's brother. That detail was taken out of the anime, which is a shame because it's a large part of why she hates Griffith so much. Like most adaptations, the anime excised a lot more content from the manga than it added so I have to disagree with your view.