Gengar EX and Gengar VMAX cards represent some of the most powerful and valuable variants available
Not the best option, but it's out there
The most notable use of the Chaos Emeralds throughout the series is to enable characters to achieve a Super form, which is represented by the Super State card in the Friends & Foes Secret Lair drop
See also: Disney Lorcana: The First Chapter Checklist and Details As far as how the rarities play out, each Rise of the Floodborn booster pack has six Common, three Uncommon and a pair of Rare, Super Rare or Legendary cards
While great together, first strike and haste don't overlap much, and on Master Piandao the ability makes it more likely Piandao will survive the attack, and on Glorybringer, haste ensured you can attack and exert it right away