Check out these IG Drawings + Schematics - they may help to explain proper designs of IG Circuitry.
Although the examples are built on Metallic Raceways + Outlet Boxes (therefore the Branch Circuits contain an EGC, or use the Raceway as an EGC), the concepts are still the same - just no need for a separate EGC when using Non-Metallic Boxes + NM-B Cable ("Romex").
as previously mentioned, a 2-Wire NM-B cable will be sufficient for a 120 Volt, 1Ã˜ 2 Wire IG Branch Circuit.
The included bare EGC in the Cable is already Isolated by design - and if the Receptacles are in Non-Metallic boxes, the Equipment Bond is also Isolated by design.
Here are the drawings:
Fig. 1: Isolated Grounding Receptacle - Termiantions details.
Fig. 2: Panelboard + Branch Circuitry detail option
Fig. 3: Overall SDS detail with IG Branch Circuitry.
These items may be found in the Technical Reference section, at this location:IG Details #1
Feel free to reply if you have more questions.