I like your lamia designs, but I feel their tails taper off after their waist too quickly. I think Lamia look better with a thicker tail and a much more gradual taper or a quick taper near the very tip.
Depends on your definition, I guess. The literal definition of a kaiju would a strange beast or monster, so by that definition lamias and nagas would be kaiju. On the other hand she isn't intended to be a "kaiju-girl" like the ones in .