Good question @dpa! The Protect Plans do not apply retroactively. As we value your security and privacy, a video will only record based on settings in your Ring app, your Protect Subscription status, and will only ever save to your account, if subscribed.
In addition to motion events or live views, and depending on your device model, your timeline might have a snapshot feature that will take still shots periodically. Check out our help center article about snapshots to learn more.
As for recordings in event history, only what is available in your timeline or event history is what will be available on your account, as videos only record when you desire them to. Any videos that occurred prior to subscription, or prior to lapse in subscription, will not be saved. In addition to subscribing, I recommend also download important video recordings as they will be saved externally to your device. I hope this helps!