Dont underestimate the post production process in rendering (photoshop). Utilizing separate passes, and masking off different materials will allow you to really dial in the details. Typically you are going to need some contrast adjustments all over the place, and I like to tweak all my materials separately.
One of the biggest things that I focus on in a white sweep rendering is the reflections. If you notice on the examples you sent. The strong highlights really give a sense of definition to the products. They convey the the curvature or flatness of a surface, as well as add in cues of material properties and visual interest. I will set up dummy lights behind and in front of products to place reflections and highlights where needed.
Below is a quick example of a rendering that shows how much post sometimes goes in. You can see how painting in some highlights and shadows creates a much more dynamic image. The product may be unrealistically shiny, but the client wanted that type of look for their packaging and displays. The darker the material, the less heavy you have to be on the highlights…
