The effect-based restrictions for the bracket system are just descriptive enough for players to get a general sense as to what falls in each category, but they are by no means as comprehensive as, say, the Magic rules or the Banned and Restricted list
The dungeons you can choose here are Dungeon of the Mad Mage, Lost Mine of Phanelver, and Tomb of Annihilation if it has been a while since you interacted with that mechanic
There are plenty of sites to help you make your choice of a good deck
So, it's possible you can trigger an effect four times with just one activation with Katara and the right mix of effect doublers on the battlefield
While the Play Boosters are likely to be printed in some capacity until the set rotates out of Standard in 2028, the Collector Boosters end much sooner, typically after the initial printing run, which will have a huge impact on card value for the variants that can only be found in this product
Fireball sorts of effects get better when theres more access to cheap mana (hence the combo with Channel early in the games history)
