Your reanimation stuff that would normally only do something with your own graveyard will now potentially target anything, such as Immortal Servitude or Obzedat's Aid
If another player gains control of Gift Shop and then visits it, they won't be able to choose a mode you chose while you controlled it
That said, you should definitely put them in a sleeve whenever you find one
Cecil, Dark Knight becomes Cecil, Redeemed Paladin, for instance, while Garland, Knight of Cordelia becomes Chaos, the Endless, and Emet-Selch, Unsundered becomes Hades, Sorcerer of Eld
Garruks Uprising in comparison to Elemental Bond is a good example of this
Circle October 20 on your calendar because Post Malones Arena Concert Event is coming to MTG Arena next week