How should I play Yuumi in Wild Rift?
Yuumi is generally played as Support. The first objective is to wins the priority by poke + sustain and avoids opposing all-ins. Its biggest edge comes from inciblable attached, massive amplification of carries and constant peel.
When is Yuumi strongest?
Yuumi takes over in mid game: synchronize with your jungler to force flashes, converted into a dragon/turret.
How do I punish Yuumi?
Yuumi can be punished when vulnerable to hard-engages and hooks if detached. A practical answer listed here is: Against Brand/Lux, avoid stacked waves and make frequent resets for resources/mana.