For Ezreal, Prodigal Explorer's draw condition requiring 'you've chosen enemy units and/or gear twice this turn with spells or unit abilities,' does this mean two separate instances of choosing, or would one spell that chooses two units count?

Ruling: You need to choose twice total during the turn. Whether you choose different permanents, the same permanent twice, with one spell, or with multiple spells doesn't matter for his condition.

Nuances:

• A single spell like Singularity that chooses two units counts as choosing twice
• Casting the same spell multiple times (like Frigid Touch twice on the same unit) also counts as choosing twice