Standard is a broken format. This is not news to literally anyone who has been paying attention. Wizards has printed a huge number of broken cards in Standard at the same time, in the same colors. As a result, we have the narrowest Standard metagame since the days of Caw-Blade. There is only one deck: Simic Food (sometimes with a splashed third color). There is only one matchup: the mirror. This article will arm you every scrap of knowledge I've gathered during the Mythic Championship preparation process. Let's begin.
Strategy in the mirror revolves around planeswalkers, protecting yours and attacking theirs. Planeswalkers generate cascading advantages, putting their controller further and further ahead each turn they're on the battlefield. In this specific case, advantage typically takes the form of 3/3 bodies: Nissa, Who Shakes the World makes a 3/3 body every turn and Oko, Thief of Crowns makes one every other turn. This means that anything 4/4 or a larger is a brick wall in combat and anything smaller than that will have a lot of trouble attacking profitably.
Once one player has had a planeswalker active for a few turns, the other will be unable to deploy any 'walker of their own, since it will be immediately lethally mobbed by 3/3s. In other words, being ahead on creatures matters, but only as a means to an end. If you need to choose between improving your battlefield of creatures and deploying a planeswalker, you should usually choose the latter. That is where the real battle is fought.