The bonus pools apply to ALL the brackets in the tournament collectively, and are shared by ALL the players in each particular bonus level.
For example, if the GOLD bonus pool is $1,000 it is available to be shared by ALL the players with GOLD designation.
The highest finishing GOLD player(s) will win the pool regardless of which bracket they played in.
For example, If two GOLD players both come in 1st place in different brackets, they will share the $1,000
The best part is you don't technically have to win the bracket. If you are GOLD and place 4th, AND NO OTHER GOLD player finished higher, you would win the entire $1,000 bonus.
The same applies to the separate SILVER and BRONZE pools.