As per The Simaris lore, Corrupted are used for tasks like defending Orokin Elites when they are in Void towers and such, they are under the control of the Neural Sentry to in a way protect them from further influences of the Void (like Wally) as well as allow the Neural Sentries which are immune like Ordis to Void exposure, not having a physical brain anymore as they are digital. The Quills and Corrupted are those that start experiencing gifts or visions from the Void, and in the Corrupted's case, this means due to the raw proximity even in a shielded Void Tower, they are antenna-ed to give the Neural Sentry direct control. I would figure part of this process would have been designed by an Archimedian of the Mind like Margulis. We are recognized as enemies likely for the Massacre on Lua if nothing else. Cephalons were often told to only take orders from particular dna types. In Ordis's case, we or the Eldar Queen know that Ordis is keyed - if he was working normally - to abandon us if we ever lose our Void abilities and thus our status as a Tenno. Lastly, the Adults didn't all die, so much as they were either overwhelmed by seeing the vast potentialities that are linked by the Void and driven mad, or being seemingly possessed as with Rell's mother in his webcomic.
So far, the Lore is not distinct upon the physical nature of the Unum aside that it is the living tower, and it links to the Quill in a similar nature as what the Corrupted are described to be. The towers are all living, Unum is the last of those towers near Cetus though, of a large number that Quill describes were destroyed by the giant sentient that was sent to stop their usage during the time of the Massacre on Lua. Much Orokin tech went to Organics after the Sentient decided to launch their surprise attack, but Ballas describes that originally the Orokin Elite mostly used defenses and weapons similar levels of technology as what the Sentient were originally made of. In-organic mind for the Sentient, but after years of flying to Tau Ceti and adapting to everything that was thrown at them, becoming self aware, adaptable and regenerating outside Void exposure much as any living creature might, and able to reproduce after their fashion. What the Sentient were originally when sent were highly adaptable drones, but not alive; though some in-universe (we have no evidence this is true) that Sentinels are in fact early evolutions of these same adaptive drones before they fully escaped Sol's rim which Early Tenno explorers found and befriended. Brought back and then experimented on by the Orokin Elite. As far as we know, the Infestation can assimilate just about anything with the exceptions of Void infused entities like us and Sentient organisms which exude energy which is outright poisonous to Infested tissues and cells. With the future seeing case, that is what I figure means that those folk have been touched or deemed chosen by the Unum, remember Saya's Vigil has Onkko decide to leave his life, his wife Saya; due to starting to see the multitude of different dimensional potentialities and timeframes before he left to become a Quill. I fully expect to see that little girl from the comics in a Quill suit in some future encounter ala seeing Little Duck in Fortuna.
Cephalons are digitized versions of people's minds yes, we also digitize folk with Simaris Scanners and seem to with our capturing folk as well. That doesn't make them unalive, just in a different state as far as trans-humanism goes. The ships themselves are made of the same kind of technocyte tendrils, tissues, and grown metal and ceramic plates as much Orokin Elite tech at the time of the Old War, so as to better go through and be linked the the enslaved Cephalon mind as described by Ordis in his hidden diary logs in the Cephalon fragments, acting largely as his replacement limbs and he feeling directly through their parts as if through normal nerves. Ordis' corruption isn't due to outside influences, though this can not be fully rulled out for some other unnamed Cephalons in the same series - Simaris said many degraded over the years - but rather the fact that Ordis's programming by Ballas never fully took, by will he has recovered and discarded his memories as Ordan Karris and decided each time that he continues to exist not due to his programming but because he actually feels he cares about the Tenno he was assigned. Ordis is glitchy because he is constantly warring within his mind as to how he should act, the loyal butler in an imitation of how he was programmed or the mercenary lord he used to be. That is why the Vitruvian being installed and returning him to a state more inline with what Ballas had programed him to be is dangerous if it reasserts in the future. While Ordis is loyal to us due to his choice to be - his Orokin servitor programming going dark centuries ago - his "Vitruvian Cephalon programming" would not have those emotional decisions. Its good for us he reasserted I would think. Apparently its not unique for Cephalons to remember who they were, as Suda and Simaris both seem to as well, though that could be due to being "Great Cephalons" or higher caste that chose such a fate for whatever reason. Suda's web comic showing she chose it due to being an Archimedian of Memory and starting to lose track of her ability to remember details. She could remember that Hunhow blew up a planetoid, but not which one anymore; so she requested conversion into a Cephalon to be free of her increasing memory loss.
All Orokin Towers are organic made of technocyte and grown tissues, what one would wonder by how Technocyte usually works, were those organic tissues grown purely or assimilated lower castes originally? There are said to be real space Void Towers in orbit around Mercury, for some unknown function, though the Grineer apparently have a significant fleet around them to prevent our mucking with such. On that topic, Unum is a Kuva Temple Refinement Tower as mentioned by Quill Onkko, each were likely tasked to roles, just as the Void Towers we visit or used to visit with our Keys. Derelicts being towers who have been overwhelmed by infestation outbreaks, if the Simaris lore is accurate due to survivors being packed on the ships and abandoned and the ships' technocyte tendrils eventually growing wild throughout the inner flesh and metals of the ship with the neural sentries lost as their power feeds are cut or consumed as happened with Jordas.