I think I figured out the answer to what the main focuses of Mega Brave, Mega Symphonia are going to be. I looked at the cards and I realized what the second moves of these Pokémon are. For Lucario, the move is Mega Brave, and for Gardevoir, its move is Mega Symphonia.

The Mega Lucario ex has a move called Mega Brave that costs two fighting energy and does 270 damage on its next turn. The Mega Gardevior ex has a move called Mega Symphonia, and it costs one psychic energy and its attack does 50 damage for each psychic energy attached to all of your Pokémon. Therefore, my speculation for these sets is that the Mega Brave set is a Mega Lucario ex based set and Mega Symphonia is a Mega Gardevior ex based set. Thank you for reading my first article. Until next time, Growlizard out!