Smoothing: It refers to the smoothness of the stream. The higher value of the smoothing is, the better fluency of the stream will be, though, the video quality may not be so satisfactory. The lower value of the smoothing is, the higher quality of the stream will be, though it may appear not fluent.
Or maybe it will have an effect on your Christmas lightsOr it may have nothing to do with image quality per se, its on the "Encode" tab... I kinda wonder it it has something to do with streaming the video over platforms like YouTube...?