Color type

I'm not sure I'm understanding your question. Any of the Color Modes can be assigned a Color Type of either Process or Spot. An RGB color can be defined as Spot and it will show as an extra ink plate in the Separations Preview panel:

If it set to Process and the document is printed, it will get converted to CMYK via color management either during Export to PDF or in the Print driver.

If you're designing for on-screen dispay only, the Colour Type setting will be of no consequence regardless of the color formulations used. Technically, RGB is indeed a form of "process" colour, and if you're designing in RGB for later conversion to something else, Process is the correct setting.