I have a smart object, and, If I apply Control "J" Or Drag It to the New Layer Icon, It will Duplicate the Layer.
And If I Go to Layer-Smart Objects- New Object Via Copy, It dose the same thing.
What Is the Different between Control J, or Go to Layer- Smart Objects- New Smart Object Via Copy.
You can have duplicated smart object layers that share a common embedded object and you can have duplicated smart object layers with independent embedded smart object. To get independent embedded object you need to use Layers>Smart Objects>New Smart Object via Copy. There are several way to create duplicate smart object layer with shared embedded object. Read Photoshop Help on smart Objects