This is the part that caught my attention - a potential huge difference between Epicurus and Democritus. Cicero's earlier reference to Democritus seems to read this ("soul and mind are, he says, one and the same thing, and this thing must be one of the primary and indivisible bodies,") as indicating that Democritus thought that there are primary and indivisible soul/mind atoms, rather than that, as Epicurus thought, souls/minds are non-primary things that are composed of indivisible atoms. Given this translation, Cicero's reading might well be a fair reading of Democritus:
QuoteSome thinkers, accepting both premisses, viz. that the soul is both originative of movement and cognitive, have compounded it of both and declared the soul to be a self-moving number.
As to the nature and number of the first principles opinions differ. The difference is greatest between those who regard them as corporeal and those who regard them as incorporeal, and from both dissent those who make a blend and draw their principles from both sources. The number of principles is also in dispute; some admit one only, others assert several. There is a consequent diversity in their several accounts of soul; they assume, naturally enough, that what is in its own nature originative of movement must be among what is primordial. That has led some to regard it as fire, for fire is the subtlest of the elements and nearest to incorporeality; further, in the most primary sense, fire both is moved and originates movement in all the others.
Democritus has expressed himself more ingeniously than the rest on the grounds for ascribing each of these two characters to soul; soul and mind are, he says, one and the same thing, and this thing must be one of the primary and indivisible bodies, and its power of originating movement must be due to its fineness of grain and the shape of its atoms; he says that of all the shapes the spherical is the most mobile, and that this is the shape of the particles of fire and mind.