When changing the target resolution of the video, Scaling type defines whether the gameplay is recorded in the chosen resolution or whether the gameplay is made to fit the target resolution after recording.
Scale Video - the video is replayed and recorded in the original aspect ratio. Aspect fit can be defined using the Aspect Type setting.
Scale Gameplay & Input - the video is replayed and recorded in the chosen resolution. The input is scaled proportionally to match the new resolution.
Scale Gameplay - the video is replayed and recorded in the chosen resolution. Input is not scaled.