At the time, the power of Planeswalkers was almost unlimited so she was able to create a host of angels (ones similar to Serra Paragon!)
However, the game's basic gameplay rules have not changed very often, as the basics of the game that began in 1999 are still applicable today
As the ability resolves, you create copies of both cards and can cast none, one, or both of the copies in any order
Other Eevee evolutions like Jolteon Ex and Vaporeon Ex, have attacks with the same Energy costs as Flareon Exs Carnelian, so you could add them to your list to evolve Eevee into
Sabrina's Gengar benefits from both that devoted base and the Gym Leader nostalgia premium that elevates all of the character-driven holos from these sets
Otherwise, setting up Celebi ex and our other accompanying Grass-type, Dhelmise can take a while, and your opponent may already be quite ahead of you by that point