Miao Ying (of the Grand Cathay) offers a unique spin on the gameplay, as do all the factions or heroes in Total War: Warhammer III. As well as balancing the running of a kingdom, Ying also needs to balance the Yin and Yan of the world, which adds yet another mechanical layer of changeable fates within the game. It feels more traditional with the archers, horseback riders, and that type of company member. Likewise, when enacting diplomacy it feels a little more natural to be having these bartering conversations to try and protect your people. Grand Cathay seems a mystical race with lots of magical abilities you can unlock via leveling up.
The Daemon Prince (Daemons of Chaos) is the latest to be revealed, and with a badass trailer as well. I found this to not only be a more interesting narrative, but also more fun to actually play. The Prince was actually from Kislev originally, but has become a God Slayer and transformed into the Daemon you control. Mechanically there are things that appeal to me more directly. Pledging allegiance to certain Gods as you progress allows you to unlock and equip a plethora of visual changes to the Prince. These change how you look, for sure, but they all have buffs and stat increases, offering a loot-game feel to proceedings.