The answer is ; white dwarfs are warmer and have lower luminosity than supergiants
The reason white dwarfs have lower luminosity is that they are way smaller in size than supergiants, even though their temperatures are way higher in comparison.
White dwarfs and red giants are formed when the hydrogen fuel at the core of the stars is exhausted. When the star is 1 to 10 solar masses of the sun, then it forms a red giant.