The speed will depend on the type of shaker available. As an example, we have achieved good results at around 900rpm with a vortex-type shaker with plate adaptor, while with an orbital shaker, the same results are achieved at 300rpm. In general, our recommendation is that the speed should be high enough to ensure the mixing of components, without spilling (after agitation there should be no traces of liquid adhered to the adhesive sheet that covers the wells).
Yes. All the ELISA references currently on catalogue are tested for both serum and plasma samples.