More than happy with this - though I think of Ravenloft as a subsection of the Shadowfell rather than vice-versa.
If you imagine a sphere around the prime material plane, then the north pole is the peak of positive energy, and the south is the peak of negative energy. Around the equator are the peaks of the elements, Fire, Earth, Water and Air in a circle. At each of these six peaks, elements are in their purest form, and as you move away from them, they start to mix with influences from the other nearby peaks. This is where the quasi-elemental and para-elemental planes come in - if you follow the equator directly from the fire peak to the earth peak, the middle will be volcanic, and most likely where the aforementioned Azer like to hang out. If you head north from the fire peak to the positive energy peak, fire gives way to light and colours and general radiance. If you reject the two dimensional nature of the surface of the sphere, then the 'concentric' circles come into play, and as you move closer to the centre of the sphere, things become more habitable, more like the prime material plane, it's just difficult to envisage. The feywild and shadowfell are therefore closer to the centre of the sphere, regions of positive/negative influence that interact with the prime. You just need non-standard geometry to imagine it all!