In order to get the maximum number of the most valuable rewards in this game, a Guardian must win 6 consecutive matches without a single loss. Doing so not only grants rewards after each match as usual but also unlocks access to a secret location called the Lighthouse that has more loot waiting for the winners.
Destiny 2 Trials Flawless Rewards are random but always within the current rotation of the reward pool, which always consists of weapons, armor, and cosmetic items.