Hello. Long-ish time wiki reader here.

[Drashner1]

What about if it was almost entirely composed of aiods in the first place? In addition, the polity might actually take an overall stance somewhat closer to Solipsism than what is generally found in standard sephirotic empires (likely being derived from the Dry Empire something similar), which combined with the fact that outside observers aren't necessarily going to be given a lot of access to the brains of minor archai for obvious reasons would mean that they wouldn't necessarily be being included in estimates of terragan population. While there might be a relatively 'small' minority of, say, 1.5e13 individuals that are willing to directly interact with the rest of terragan civilization, their claims of being part of a much larger tribemind-based metaempire could very easily be dismissed as being memetic engineering from the ruling archai.

I'm not entirely sure what you're asking re these beings mostly being Aiods. That would make no difference in terms of the amount of computronium needed to support an S3 mind.

I'm also not sure what you're asking re population. Can you explain a bit more what you're referring to here, please?

Thanks!

Todd