Beorn has power but it is mortal based IMHO. Bombadil I believe is a spirit of the earth... a lesser Vali as described in the Book of Lost Tales part one... The Coming of the Valar...
About them fared a great host who are the sprites of trees and woods, of dale and forest and mountain side, or those that sing amid the grass at morning and chant among the standing corn at eve. These are the Nermir, the Tavari, Nandini and Orossi, brownies, pixies, fays, leprawns and what else they are called for their number is great, yet they must not be confused with the Eldar, for they were born befor the world and are older than its oldest and are not of it but laugh t it much for had they not something to do with its making.