How do Red Velvet's different "Red" and "Velvet" concepts influence their music evolution over the years?

[alexalbon23]

I’ve always been fascinated by how Red Velvet splits their music into “Red” (bright, pop) and “Velvet” (more mature, R&B). Do you think this concept has helped them evolve musically, or does it limit their creative potential? Any examples of songs where you felt they blurred the line between both concepts?