Natures
Mild raises Sp. Atk by 10% and lowers Defense by 10%. It is applied at the very end of the formula, after IVs and EVs, so the higher the stat, the more the nature gives and takes.
Sp. Atk at the cost of Defense. Sensible for something that will not survive a physical hit anyway and wants to hit harder.
Flavor
Likes Dry, dislikes Sour. This matters for Poffins, Pokéblocks and Berries: a Pokémon eats a disliked flavor reluctantly, and healing works worse.