Though Collector Boosters will be sticking around unchanged, the main method of pulling and collecting MTG cards will be much more streamlined overall
Rather than preserve Heartfire Hero from removal, this deck employs Callous Sell-Sword or more accurately, its adventure side to proactively kill it off on your terms
Chaos: Whenever you roll Chaos, look at the top six cards of your library
It's definitely a strange ability, but the gist of it is that connecting with your 3/3s will let you cast powerful spells for free, which will likely make it even easier to use Magar and connect in combat as the game goes on
You can use this ability to manipulate your +1/+1 counter distribution, spreading counters across your board and drawing as many cards as you can
Game knowledge helps you out here, understanding what your opponent is looking for or wants makes it easier to make your decision on whether to keep the Life card at the top or move it to the bottom