RGH and flashing your DVD drive are 2 very different things. Flashing your drive will allow you to run burnt games nothing more, RGH allows you to run unsigned code.
The nand x is used to read and write the xboxs nand, I believe it programs the coolrunner also.
The coolrunner is used to glitch the xbox allowing it to run unsigned code.
I have never done a RGH, I think all you need is a coolrunner and a nand x. If you just want to flash your DVD drive I recommend buying an xecuter X360USB Pro. the X360USB Pro is used to connect your DVD drive to your PC it reads and writes the DVD firmware. You will also need a way to power your DVD drive I myself use a maximus power dongle, most people would recommend a xecuter ck3i