Game view resolution set to 100x100 and 240x240

I am trying to change the render resolution between these two values. However I would like the view to “best” fit into the window.

So for example if the windows was 640x480 and I set resolution to 100x100 I would get a 400x400 sized image with at a resolution of 100x100 (EG 4x4 identical pixels), with black bars fillinf the rest
and for 240x240 I would 480x480, but at 240x240 resolution so 2x2 identical pixels, again with black bars.

The resolutions I use wont always be sqare, for example I might use 100x240. Basically I want it to be that resolution, but I dont want it to be that “size” on the screen. Adiditionally it will change at runtime.

Not sure how to go about this in Unreal. Any help is really appreciated as I am pretty new at unreal!

I ended up using ASceneCapture2D, capturing the scene to a RenderTexture and using that RenderTexture into a UMG widget. That widget HUD I placed over the screen so that is what I saw. I set the desired resolution of the RenderTexture to the desired render resolution. Then I scaled the image on my HUD to fit my window.