How have the Shadar-kai changed over the editions and is there any consistency to be found in the lore between editions?

In D&D 5e, the Shadar-kai are a sub-race of elves. However, it seems that in 4e, the Shadar-kai were humans. In both cases, they lived in the Shadowfell and served the Raven Queen, so it doesn’t seem likely that they are two separate peoples; rather, they are supposed to be the same "race", despite being human in one edition and elven in the next.

I believe they were also in editions prior to 4e, but I’m only going by the Forgotten Realms wiki page, which seems to claim that they were a kind of neutral evil fey creature in 3.Xe (but generally the information on that page appears to be a mish-mash of conflicting lore from various editions, which is kinda the point of this question).

This is confusing to me; I’m not sure if it’s possible to extract any consistency out of this, but if it is possible, I want to ask:

  • For each edition of D&D that the Shadar-kai appeared in, what were they? Human? Elf? Something else?
  • I’d also be curious to know, briefly, what they were like, since in 4e/5e they live in the Shadowfell and serve the Raven Queen, but in previous editions the Shadowfell/Raven Queen didn’t exist, so what were they all about instead? Again, only very briefly, since this isn’t the main point of this question.
  • For each of these editions, is there any official lore justification for why the race changes? Or is it more like the previous lore was just disregarded and overwritten (such as in the case of 4e -> 5e, where 5e just seems to forget that they were ever human in 4e)? Again, I’m looking for in-universe lore, not designer-reasons.

Since the Forgotten Realms wiki has confused me, I would prefer people to cite from official source book and Dragon magazines and similar, rather than wiki websites like that one.