The weight of the diff fluid depends more on what your doing with the vehicle, what surfaces you run on, and your driving style. More personal preference than anything.
The weights you mentioned are OK, yes. Those are weights I would run if on a high traction surface in a racing type application. I mainly bash and prefer heavier weights to get more of a locked diff feel but again, it's personal preference really. I use silicone ear plugs instead of diff fluid in my 6s Notorious and 8s exb outcast.