The line "we are ancient" probably refers to the Consult or the Inchoroi and their inheritors, not to the Skin Spies specifically.   They're likely a recent creation of the Tekne and probably derived from humans, albeit with considerable changes.

One should remember that the Inchoroi didn't want to create large number of souled beings.   That they are incapable is purely our projection on the text and contradicted by the existence of rare souled members of the Weapon Races.  The Wracu, unlike the Sranc or Bashrag, would in exist in numbers small enough that their possession of souls wouldn't endanger the plan.   There's another data point in favor of them having souls, namely the conversation Akka has the with scalpers in The Judging Eye.  A dragon would choose to withdraw from men it didn't want to confront instead of being driven by its instincts to fight them.

Bakker has mentioned that some apes and whales as well as a the rare Sranc or Bashrag have souls.  Sranc and Bashrags have language and tool use, but are ruled by their instincts and appear to have no capacity for introspection or reflection.   Wracu seem, like the Inchoroi, to possess similar instincts (plenty of sadism is on display in their interactions and they seem to love cruel word games) but can choose how they act.  They seem tied to the No God by allegiance to a common cause, not puppets that the No God can shout through.

The Wracu are clearly an engineered race, but one based on a template created by high level biological mastery and then derived using cruder methods and selective breeding.  They are unlikely to be "cybernetic" as opposed to having a biology that concentrates iron in the bones and so forth.  They are also products of a people who know about the Outside and have technology that can contact it to some degree but do not have sorcery.   They are likely something like biological warmachines connected to the Outside.

It is also important to remember that Chorae do not salt practitioners of the Psuke.  The Psuke is close enough to sorcery that the Chorae still block it and are lethal to its practitioners, but the effects are not the same.  The Wracu are likely close enough to sorcerers that Chorae are mildly toxic to them.

With regard to the issue of killing Kelhus as Daglaish, recall that the Consult intends to have two of his children in the possession of their Nonmen allies at the time.  Even if they do kill him, their will be multiple survivors of his bloodline.

Hmm... very interesting. Even then, we should ask why Chorae would burn rather than Salt a Cishaurim.

Chorae are products of the Aporos, which is to say language based sorcery where meaning is of crucial importance.  Cishaurim don't die in quite the same way as sorcerers because the Psukhe isn't quite sorcery, but its so very close to sorcery that interaction with the Chorae produce similar but not identical effects.

As for Nannaferi, she seems to be a walking pinhole in the veil between the World and the Outside through which Yawter can pour some of her power.  That might not be a terribly accurate metaphor because we don't have really bright and well educated characters giving detailed discourses on this subject, backed by millennia of scholarly works at this point in the series but since Mimara is a viewpoint character and she is likely to be around Akka, we may get this in the No-God.  The book is scorched in the same manner as Nannaferi grows young, she receives premonitions of the future, and Meppa is healed.  Yawter acts through her, changing the world without sorcery. 

A few additional points.  One, I don't think the Aporos and Tekne are closely related, although the Tekne clearly does have the ability to interact with the supernatural.  Like all interacting forces, its possible they can be combined or come into conflict (Chorae and Wracu) but that doesn't make related arts.

At this point I'm inclined to believe that most, if not at all, of the "theurgic" or divine sorceries used by the likes of Psatma and Porsparian are simply a different application of the Water.

This isn't true because we've seen Psatma handle a Chorae, specifically the one she used to destroy the Swayal infiltrator.  Something that clearly isn't sorcery is at work. 

[EDIT Madness: Fixed quote tag.]

Moe Sr. gets salted by Cnaiur.

No, he burned although that might be because he was so weak in the Water.  TTT page 387  "Moengus gasped, jerked, and spasmed as Cnauiur rolled the Chorae across his cheek.  White light flared from his gouged sockets.  For an instant, Cnaiur thought, it seemed the God watched him through a man's skull.

What do you see?

But them his lover fell away, burning as he must, such was the force of what had possessed them.
"Not again!" Cnaiur howled at the sagging form."

Bolding is mine.  He burns, he does not turn to salt, and his body sags.  Now Inrau also doesn't have the typical Chorae reaction, but he was barely marked and we all know Moenghus was weak in the Water. 

Page 378, Proyas hits one of the Incandanti with his Chorae.  "Then a flash, a black-ringed circle light, from which the saffron figure plummeted like a sodden flag."  It's unclear exactly how the Cishaurum dies, but the flash of light and the death are consistent with Chorae-sorcerer interactions.  It's clear that the Psukhe isn't quite sorcery, but its close enough as far as most things are considered.  Obviously, the eyes of the Few disagree and the judgement of the God of Gods remains to be seen.

Thank you and I agree with your points as well.  The appendix describes the Psukhe as "arcane practice . . ., much like sorcery", which is to say much like sorcery but not sorcery.  Crucially, the Psukhe does not employ language and depend upon meaning for its strength, instead being based on intuition and being fueled by passion.  It too is acting on the same metaphorical principles (walking on the echoes of the ground, its compulsions only working on beings with souls, etcetera) and its users are as vulnerable to Chorae which means even though its technically not sorcery, it is pretty damn close. 

And you're right about the Tekne too.  I had initially thought, way back during the first trilogy, the No-God to be some unholy improvisation of the Tekne and the Aporos.  The sorcery of negation seemed like a good fit for a barrier to souls entering the world, but when we learned that genocide wasn't the Inchoroi's reaction to learning they could be damned once they were stranded on this strange world but instead the whole reason they came to Earwa in the first place, my perspective shifted.  Dragons, products of the Tekne that they are, are clearly partially supernatural in nature.  The Inverse Flame is another piece of high technology that touches on the Outside and, of course, the No-God.  It makes sense.  If physical world and the Outside are connected, if their is interaction, then that means that physical actions can in some way interact with the Outside and technology can be the producer of those actions and effects.