That means Standard Brawl uses the current Standard card pool, while Historic Brawl includes all cards on the platform
(Equal to the other five colors.) The booster distribution of purple is 1/6th the rares, 1/6th the uncommons, 1/6th 10 of 11 common slots, and 100% purple in the 11th common slot
Im no expert on Goats, so if you want to get your Goat tech fresh from the source, check out @goattribal on twitter or I have dabbled in goat-mancy before, though
The major players in Standard right now appear to be Reanimator, Jund, Bant Control, and various flavors of U/W Midrange, with and without red
It's at minimum worth two +1/+1 counters on each creature you control, and accounts for any counters your creatures already had
These have different outputs, but they're still fresh enough off the presses that they could climb up this list in time, or drop off completely