RAW files are not stored as normal RGB files. They use the bayer grid or other encodings.
So, the files have to be developed for display.
Yes, but the Raw file in itself does not take into account the user's selection (auto, sunny, tungsten...) but when shown "as is" the user's selection is applied to the original data and displayed on screen. In the EXIF data you find the user's choice (sorry French version of GC.
Lightsource: Tungsten (Incandescent) or another
Lightsource: <unknown> if the camera was on "Auto" mode concerning light.
And farther down you will find a list of color corrections:
---- SR2SubIFD ----
WB RGGB Levels Auto: 2660 1024 1024 1272
Niveaux BB RVVB: 1428 1024 1024 2688
Color Matrix: 1406 -391 9 -42 1356 -290 22 -53 1055
Niveaux BB RVB daylight: 2316 1024 1516
Niveaux BB RVB Clouds: 2504 1024 1392
Niveaux BB RVB Tungsten: 1428 1024 2688
The first lines are there to correct the "quality" of the Bayer filters and are those applied if you choose the "Auto" mode on the camera. Auto mode on the camera is named Light Source : <unknown> in the EXIF
When I use LR and choose "Auto" instead of "As is", the same image is displayed whatever light source I have chosen on the camera. This is why I believe that the RAW image data does not take into account the user's light source selection. And we can therefore change this after on the computer.
N.B. I use a Sony A7ii and I don't know if all camera manufacturers give the same information in the EXIF part of the file.