In short:

 You can select and Hype Up your favorite Superstars.
 You’ll also gain extra Feud Warscore on defense.
 Superstars with Class Advantage will gain a large boost to their Hype Stats.

 Initially, All Superstars will have the same benefits at each early Hype Tier:
 A random C Tier and a random S+ Tier will have equal base values for Awareness, Aggression, Toughness, and Kick‑Out Bonus when both at Hype Level 1. When stats are equal against each other, they basically zero out.
 For Awareness, a tie between opposing stats goes to the non‑AI player.

In detail:

 In all matchups, Superstars will get a boost to all Hype Stats when facing the class they are strong against
 If you take a Hype Level 1 Striker against a Hype Level 1 Showboat, the Showboat will go first because their Awareness Stat is boosted making it higher than yours.
 If you take a Hype Level 2 Striker against a Hype Level 1 Showboat, you will go first because the Hype Level gives a bigger increase than the Class boost.
 Assuming equal talent, trying to beat a Hype Level 2 with a Hype Level 1 will be extremely difficult. That’s because of their increased Toughness, Awareness, and Kick‑Out Bonus Stats. But, taking a Hype Level 1 Superstar with a Class Advantage will improve your chances at success, giving players a difficult but still doable route to overcoming a Hype Level disadvantage.

 For these lower tiers, you can expect up to a NET ~30% total damage and defenses for each difference in Hype Tier, and upwards of ~50% with class advantage.