The ADuM5x1x and ADuM6x1x parts offer less of an EMI challenge than previous isoPower devices. The main reason for this is that the new parts are targeted at lower total power, so the peak currents in the tank oscillator are lower. At very low load, (<3mA) the part may not need any mitigation at all. Above that level, you should read and follow the recommendations in AN-0971, however reduced levels of stitching capacitance are required to achieve the same EMI goals.
For more information: www.analog.com/an-0971