How can I offset the camera view on my actual screen?

Hello,

I’m working on a platform game with a resolution of 19201080 (16:9). Now I want some space at the bottom of screen for a completly opaque UI, so I only need 1920800 for actual gameplay area.

An desired example would like this:

However if I only set the camera ratio to 2.4:1 (1920*800), it would be like:

I want “offset” the camera 140 pixel up to align the top. but I could not find a proper method. Is there a common way to achieve this?

Of course I can keep the camera 1920*1080 and instead moving the viewport I move actor in the scene, but that’s another thing I’m not sure: will there be extra cost? does things below UI still get rendered?

Any suggest would be much appreciated!