Starlight is usually used to describe the shining light in the starry sky at night, giving people a bright and magnificent feeling. This word often appears in poems and literary works to describe the beauty of the starry sky.
On the other hand, Starlight Glimmer is more commonly used to describe some bright and flickering objects or scenes. For example, the water surface under sunlight, the shining light of gems, the brightness of flames and so on. This word pays more attention to describing the bright and flickering effect of the object itself.
To sum up, Starlight Yu Yu is more inclined to describe the beauty and magnificence of the starry sky, while Starlight Glimmer is more used to describe the flickering effect of other objects or scenes in bright light.