iCloud Photo Library, when it fits your needs, is a great way to avoid having to manage where your images and videos wind up. You capture video on your iPhone or drag an image into Photos in macOS, and it just syncs everywhere while making a central copy at iCloud. While I hear regularly from people having difficulty with aspects of it, it's a way to reduce the stress about how much storage you have on any given device, especially iOS devices.
(And, yes, once again: if you delete an image on one device that's linked to iCloud Photo Library, it deletes it everywhere. Apple's warning when you try to delete is real.)