smoke is usually for terts that would look like ass otherwise, like a really dark color on really bright ones (black on leaf, for example). it's when you want to diminish the tert a bit. it would look nice on your dragons, but since the terts are nice go for something more stand-outish

at least, in my opinion

gembond is usually a go-to gene, but I second underbelly. both would look good, though, so pick whichever you like more