I find Gold ore-berries down close to bedrock. I don't know the specific range, but I also find essence-berries there as well.
BTW, I've grown ore-berries on the surface, but they do grow better in darker caves. I have mine illuminated to BL:9 in the darkest corners to curb mob-spawning.
I process all my berries (except essence) in a smelter. Smelter ingots seem universal, as long as the metal type is known by the target tech.
BTW, the only use I've seen for essence berries so far is from a video where the host used some king of "Queen Grub" to spawn glow-worms, Essence berries were the queen's food. Anyone have other uses?