Other than relative temperatures, is there any difference between a red sun and a yellow sun?
No.

Small red dwarfs may be fully convective. Larger stars like the sun have a region in which the energy is transferred by radiation. So in small red dwarves, the star becomes fully mixed.

Red Giants are quite different and are large and old stars, swollen by their powerful cores.

Both red and yellow stars produce large amounts of neutrinos. Yellow stars produce more than red dwarfs because they are more powerful. Red Giants would produce more than yellow dwarfs, as they more powerful.

Nothing that could explain superman.