There's a lot of ways to build mana bases, and many different possible configurations that you can use
You can make, in Mono-Green alone, 1/1 Squirrels, Insects, Saprolings, 2/2 Wolves, Bears, 3/3 Centaurs, Elephants, Beasts, from Squirrel Nest to Grizzly Fate to draw tons of cards
If you combine this with the Mastery Pass, you get more packs when you battle through those challenges and events
Defense Grid conveniently has a pretty solid matchup against all those types of interaction even holding its ground against Force of Vigor being a pain to remove or protecting your The One Ring through Blood Moon
Technically there are better games which have less luck or greater subtlety despite more simple mechanics however I find these all tend to be a lot less enjoyable
The tournaments vary in scale, ranging from local Premier Challenges to state-level Regional Championships and finally the large-scale National Championships