Yes, Southern AG Triple Action Neem Oil is labeled to treat whiteflies.
The manufacturer of Southern AG Triple Action Neem Oil lists the precautions on the product label for safety reasons and is pretty generic for most pesticide products. As long as you are applying as directed and avoiding skin contact it is safe when used as directed. They just want to make sure they are covered in case someone does not follow instructions. As long as you wash edibles before consuming it is safe to use.
No, there is no need to add soap to the mix of Southern AG Triple Action Neem Oil with water. Some soaps can also be ionic and harm plants that are sprayed.