Is my storage counted per album or across my whole account?

Across the whole account — it's one shared allowance, not a per-album bucket. The Album Edit page will tell you any individual album's size, and the account meter sums everything together. So the accounting question that matters is "how big is everything I've ever uploaded," not "how big is this one wedding." If you're planning a season of 500 GB events, do that sum before you commit to a 100 GB plan.