Well, as you know, Gwen came back in the Clone Saga. After that, we didn't see her again until the two last issues of War of the Symbiotes. In that arc, Venom assimilated completely the symbiote in her, and all that was left was a perfect molecular copy (as in, not a clone) of her body with all of her memories.
As for the changes in look, I sincerely don't know. But in her few appearances since her revival, Gwen was always lost, confused, something understandable after dying and getting better from it, I suppose. Before Ultimatum, I don't think I could have imagined her with a dress, yet she wore one. All in all, it seems like her death experience has "softened" her, making her less punk (she still is, to an extent : she has a face piercing and the cover for issue #1 shows her with worn out jeans) than before. There is also the headband that really makes her look like her 616 counterpart, and the fact that here eyes went inexplicably from amber colored to blue colored.
There are places where he seems to be all right, like the opening shots with Mysterio. That was some good stuff. Though after that it just didn't do anything for me. Spider-Man's head is gigantic and when he puts the costume on suddenly he looks like he's a ten or eleven year old. 
