How many albums can I create? Is there a cap on the paid plans?

On the free plan you get exactly one album, full stop. On the paid plans the limit is effectively unlimited — the create screen literally shows your capacity as something like "14 / ∞" once you're on a paid plan. For a working photographer that means you can run every wedding, every pre-wedding shoot, every birthday and every corporate event as its own separate album without ever counting them nervously. The constraint that will actually bite you is storage space, not album count.