Displaying the gameview in a box in the viewport

Hello everybody,

is it possible to create something like the following interface/screen? (A box with the 3D game view within)
Or is it possible to create a camera view that don’t centralize in the middle and where i can fade out the unused parts of the camera view?

The things I found that want to archieve something similar is Change viewport size on mobile - UI - Epic Developer Community Forums , but it wasn’t answered.

Kind regards and thanks for your time,
Banjoboy