As for the 13th slot in the pack, it is a guaranteed foil card, and it can be of any rarity yes, you can even get a mythic rare foil
These are the only two Legendary Creature cards in the deck with the Esper combination, which allows them to run as the decks commander for reference, a Creature card like Emet-Selch of the Third Seat is a Dimir card, which would disable the usage of all White cards in the deck though he would make a great Commander deck in Magic: The Gathering
it's a lot worse in decks that can't convert a double Boros Charm into a kill
Primal Vigor Primal Vigor is almost like Doubling Season except it wont work for planeswalkers entering the battlefield, and it's a symmetrical effect
Most of these cards fall into a Treasure/Clue/Food subtheme the deck has which doesnt particularly suit the final product, while The Day of the Doctor and Run for Your Life are just plain bad
Box set: Sets with a predetermined batch of cards, where what you get is not randomized