As you pointed out, the difference between Pokmon EX and Pokmon GX is that the former ones are always Basic whereas the latter ones are always the stage they are supposed to be [1] (except for Tag Team GX cards which are also always Basic)
Inverted by Wigglytuff's Do The Wave attack
There's not a ton of other reasons to seek out this product, so Steam Siege is a great example of a set you'd be better off buying singles from, rather than shelling out the money for the sealed product
Number 35: Ravenous Tarantula and Number 84: Pain Gainer have very similar designs and the same stats, but differ in their effects and being one rank apart (35 being Rank 10 and 84 being Rank 11)
However, the Melmetal ex Battle Deck comes with more than just the cards themselves
In this guide well go over the best decks for the Alcremie Drop event in Pokmon TCG Pocket , and all of its missions, tasks, and rewards