adjust camera or view to different resolutions

I’m trying to make a level chooser scene in my project, but cant get around different aspect ratios. Now the problem is not with textures in GUI(at least not yet :)) but with camera, or field of view.
My screen is divided in two sections. GUI is on one side, and 3d objects are on the other side. In editor I’m working in 5:4 ratio, but when changed to, say, 16:9 all my objects, that were filling all desired space in 5:4, are now cramped near center of the screen due to more screen space on both sides.
Now is there a way to fix this? I know i can get the right-most object in the scene, get its screen position and adjust camera position.

(if (object.Screen.position<Screen.width)
{move camera until object.Screen.position+10 >= Screen.width}

But moving camera to the right will increase empty space on the left, so that is not the best way to do this. I could bring camera forward, but then my "“level objects” will go out of view on top and bottom.
There is this way to do this:

But i dont want to crop the view space. Is there a way to do this?

5:4 Aspect ratio is ok. Objects fill desired space.

16:9 aspect ratio: Free space on both sides. What to do?

Take a look at this blog post, maybe it helps.