Contents-
Arceus- nothing special, other than it looking freaking epic.
Diance- Rock/Fairy mystery legend
Floette- cool pattern, I would catch it.
Latias- It appears as a mega Latios, but it's name says Latias. She might not get a mega. Possibly a Latiosite will be used.
Volcaneon- Fire/Water mystery legendary
Vivillion- cool pokéball patter, probably given out in an event
Latios- Latios in it's mega form
Hoopa- Psychic/Ghost mystery legendary
Vivillion- Another design for it’s wings, but i can’t quite tell where it’s from.

Warning, story spoilers:
The Floette pattern is the same as the one owned by AZ, as seen in the flashbacks and at the end of the game when it returns to him.