Hi, CuriousMB,
Welcome to the Apple Support Communities. It sounds like you have some concerns regarding your videos and other content on your iPhone. We'd be happy to help!
If you're using iCloud Photos, pictures and videos you delete from your iPhone (or other Apple device) are placed into a Recently Deleted Folder. They stay in that folder until either you permanently delete them from the folder or 30 (thirty) days have passed: Delete photos on your iPhone, iPad, and iPod touch - Apple Support.
In either case, once the pictures and videos are permanently deleted, they are no longer accessible, unless you have a copy saved in another location.
For more information on how Apple handles your data in iCloud and in general, check out the following information:
iCloud security overview - Apple Support
About encrypted backups on your iPhone, iPad, or iPod touch - Apple Support
Privacy - Apple
Legal - iCloud - Apple
Legal - Apple Privacy Policy - Apple
Best.