That's interesting. I think to a degree you can even see that shift inside Tolkien's works. In the Hobbit, the elves are actually portrayed as playful, mischiev

That's interesting. I think to a degree you can even see that shift inside Tolkien's works. In the Hobbit, the elves are actually portrayed as playful, mischievous and a bit fairy-like (in particular in the Rivendell chapter) whereas in LOTR they changed into graceful, deeply serious superhumans. ...of course it might also be that the elves in the "Silmarillion universe" i.e. today's Middle Earth were always like the latter, and the playful elves from the Hobbit where another glimpse from the hypothetical "standalone Hobbit universe" before the Hobbit got moved to Middle Earth.