Spoilers below
Aren’t most of those said explicitly? Also the Whishes seem mostly born from different kinds of wishes, Echo from a falling star, Phillip’s from a wishing well, the 100 cranes from, well, the 100 cranes Owen folded (y’know, that legend thing), Halley I think is a dying wish and the lady from the lake is either a mother’s wish or a dying wish as well (or both?). The remnant is probably a suicide wish, maybe it’s a corrupted Echo or Euca made another wish later; I’m pretty sure it’s his considering in Jinny’s flashback Euca is seen hanging and the remnant literally having a noose around its neck (considering time and memory shenanigans I’m not even sure wether or not either one is from this “timeline”’s past).
Where their strenght lies and its extent also seems strongly related to the means of their creation, like how Echo is stronger when there’s a meteor shower or how Cecilia’s is weaker away from her lake.