I saw your answer about Ghosts vs Fae, and wholeheartedly agree. As a follow up, do you consider Leprechauns and Elementals a faction of the Fae or separate entities altogether? I have a significant Irish heritage and my grandmother would always warn us not to go into the cornfields at night lest something take a shine to us and wish to take us 'home'.
Leprechauns definitely fall under the category of the Wee Folk. Most of the descriptions of them in folklore literally refer to a small man in red or green, and some source cite them as part of the Tuatha Dé Danann. Popular folk tradition describes them as solitary fairies with trickster tendencies and I know of at least one place where they’ve been associated with a local barrow, though the name is escaping me just now.
Elementals, on the other hand, are just that - elemental. Beings derived from or made from the elements do not seem to belong wholly to any particular group other than the overarching types of themselves, if that makes sense. There are certainly elementals that dwell in forested places or in bodies of water and I think these can be mistaken for types of Fae, but I consider them to be a separate type of entity, without particular allegiance.
And speaking from personal experience, tree spirits are heart-stoppingly awesome. They seem to be either beautiful and serene or grouchy and terrifying, and I have yet to encounter anything that falls in between. 😅
