Mass removal is usually temporary or conditional in blue
Additional creature cards discarded beyond the first won't result in additional Moogle tokens, and additional noncreature cards discarded beyond the first won't result in additional counters
Each deck can have one or two Ink colors, so I imagine Amethyst will be a popular choice to pair with one of the others, if only for the card draw options
Izzet is widely considered the strongest or one of the strongest archetypes, which means you will have lower-quality Izzet decks when you're contested for the cards
At the time of writing this, all Promos released so far are obtainable from The First Chapter set, just without the special rarity stamps put on the cards
This focus can be seen on cards like Emet-Selch, Unsundered