About the dimensions. A movie with an aspect ratio of 4:3 (fullscreen) will use the entire image and won't have black bars (and can't be anamorphic). A movie with an aspect ratio of 16:9 can be non-anamorphic (not strectched, black bars) or anamorphic (vertically stretched, no black bars). A movie with an aspect ratio of 2.35:1 can be non-anamorphic (not vertically strectched, big black bars, see picture 1) or anamorphic (vertically stretched, smaller black bars, see picture 2). As you can see in the anamorphic image more space is used for the actual picture because it's vertically strectched (won't be vertically stretched on playback ofcourse) and less for the black bars -> better image quality.
Picture 1.
Picture 2.
