@Michal211a 

Hi, 
Currently, the Tapo app doesn't support changing the email account directly, but you can refer to the following steps to change the email address for your camera.
    1. Log out of the current account by navigating to the Tapo app > Me > View Account > Tap Log Out. Alternatively, you can uninstall and reinstall the app, then log in with the new account (new email).
    2. Factory reset your camera and reconfigure it on the Tapo app, and it will bind to the new TP-Link account(email address).

The cloud video clips are stored under the TP-Link account, and they can be stored for up to 7/30 days according to the Tapo Care service you subscribed to.
If you don't delete your TP-Link account, these cloud video clips won't be deleted unless they have reached the 7/30 days retention period.
On the Tapo app, if you log in to the Tapo app with the old account, you can go to the Cameras tab>Cloud Activity page, select a date, and watch the existing video clips.

Best Regards