The white balance in evo works like in digital cameras or photo software (e.g. RAW converter). With white balance, you set the point that should appear as white in your image (white point https://en.wikipedia.org/wiki/White_point).
If you set the point to 2,700K and have lights/lamps at 2,700K, a white wall will appear white in the photo/rendering. If you set the white balance to 5,000K with the same light sources, the white wall in the photo/rendering will be yellow/orange. You are not changing the light of the light sources with the white balance, but the "color" that should be white in the image.
Generally, the white balance is set automatically to make the scene look realistic. But sometimes the automatic adjustment may not be possible. This depends on the different colors and textures used in the project, for example, for wood-brown floor textures.
White balance can only be changed for the entire floor and not for a specific room. Unfortunately, there is no workaround to adjust the white color in a room that is different from the other rooms.