Paddle keeps sandbox and live accounts completely separate, and so does PaddleSubs. Products, prices, discounts, customers, transactions, Access Subscriptions and licenses all belong to the environment they were created in, and the Environment option decides which one your site uses. Everything from the other environment is hidden, on the administrator pages and on the site, until you switch back.

User groups are the exception: they are Joomla's, not PaddleSubs'. A test purchase in the sandbox adds real groups to a real account. Remove them, or delete your test accounts, before you go live.