After reading the book, and looking at the pictures that are there, I have to agree, that there was likely more than one style of the robes done. The beautiful full shot of the guard Doesn't look like a ROTJ guard to me. It looks more like the AOTC guard with the way that shoulder overlaps. The under robes in this picture are also very clearly the same color. Which they are not when seen on screen, or when you read her description.
In the book she mentions that the helmet is held to the robes by a dog collar clasp, I'll bet that is how the drape was accentuated. I am NOT advocating attaching the helmet to the robes as that boarders on suicidal. But pinning up the shoulders should help to do the same.
In my robes I created the drape affect by having elastic go 3/4 around the neck whole leaving the front loose.
For lack of a better picture You can see mine with the waves, while my partner has vertical pleats
The argument can be made that there are references to both wave, and flat. Like wise there is plenty of evidence that shows yes the guards wore red visors, however there is plenty of other lucasfilm approved images with black visors.
The boots are never shown on screen, So I honestly dont care and would rather wear black, despite my red ones.