Have you got a sand substrate? Cories really should be kept on sand. Six or eight cories of one species is fine.
I think the danios might upset the hatchets, as they're both surface dwellers, but the hatchets are very sedentary and the danios very active.
Neons would do better added further along the line as they do seem to like mature tanks, even if you've done a fishless cycle, but both they and dwarf rainbows are suitable for your size tank.
Do you know how hard your water is? Neons do best in soft and rainbows do better in harder water. Personally, I'd pick the one that suits your water and have a larger shoal of those.