Do triggered abilities without 'may' have to trigger, and must you choose a target if one is required?

Ruling: All triggered abilities always fire when they meet their trigger condition, regardless of whether they have "may" or not. The "may" refers to choices made during resolution, not whether the ability triggers. If a target is required, you must choose a valid target.

Sequence:

• Triggered ability fires when condition is met
• Target must be chosen if required
• On resolution, "may" effects allow you to choose whether to perform the action

Nuances:

• In the Yasuo example with a deflect unit, you must target the unit and pay the deflect cost
• There are known issues when you cannot pay required costs (devs are aware)
• Examples like Reaver's Row require declaring and choosing a target, but "may" allows choosing not to move on resolution
• Examples like Flame Chompers and Immortal Phoenix always trigger, but you choose whether to pay their costs on resolution