How many products can I add?

Your plan sets how many published products you can have; drafts are unlimited. At the cap, publishing another is blocked and the message shows your limit — save it as a draft, unpublish another product, or upgrade under Account → Subscription. If your store has more published products than the plan allows (for example after moving to a smaller plan), shoppers see your oldest products up to the limit; the rest stay in your admin until you unpublish some or upgrade.