What happens on day one of the trial?

You choose a plan and enter a card before the trial starts, so nothing is charged and nothing is pending. The fourteen days begin immediately and the whole product is open: the statement, the cost engines, Insights, exports and the connectors your plan includes.

Nothing is charged until the fourteenth day ends. If you cancel before then you are not billed at all, and you keep access to Settings and Support so you can export what you built. What you enter during the trial is real data on a real account, not a sandbox that is thrown away afterwards.