I am back with my Results,
It was indeed caused by anchors.
Here is my Setup, Little bit Different, I am using Canvas Panel (With Fill Screen as Size) First then Size Box as Child and Followed by Horizontal Box and Images.
Before Setting Anchor Properly it was stretching UI in Movie Render Que but not on Viewport
However after Setting Anchors Properly (Setting it to Fill and Adjusting Size) it was Perfect (400px Height and 1920px width) as it was on Viewport and Movie Render Que
Here is Viewport Screenshot
And Here is Result of Movie Render Que after
I hope it Helps