In our former fearsome CB foursome (Kompany, Otamendi, Stones, Laporte) I actually had Stones as the weakest passer on a pure technical level, with Laporte at the top and Kompany not far behind. Stones however is/was by far and away the smartest passer, especially at breaking the lines which I would argue he's as good as if not better than any CB on the planet on his good days at, as well as his ability to control things from ultra deep in a sense. It can be tough to see it at City, especially compared to Laporte but at the World Cup his vertical passing was streets ahead and very apparent.
Laporte and Kompany have/had great technique but their M.O is more in their ability to play big long cross field passes and they generally needed a lot of power in their passes to break lines, especially Kompany. Otamendi stylistically was a cross between Stones and Kompany, albeit not quite as good as either at their strengths but probably better at their weaker passing traits.
Dias is apparently a good passer, but from what I know he's more of a Kompany type than anything, but with maybe more subtlety. We haven't seen much of it yet but it might be because he's new. It does take time for most Pep signings to adapt and show the best of themselves.
Aké I don't know. I assume with his academy training and playing under Eddie Howe he's better than your average CB but I've honestly not seen enough of him to tell. He's not been up to much passing wise in the games I've seen him but I might put that down to a certain timidness and similar needing to adapt like Dias rather than inability. I think we should be cautious overestimating his passing abilities until we see them, but I won't be remotely bothered if Dax is right on this one.
I think Garcia's very good too, not too dissimilar to Stones but obviously not on his level (yet?), but I don't think people tend to enjoy discussing Garcia much so I'll leave it there.