I guess that the Darkhive (like so many other of my settings) is technically "post apocalyptic". The only difference is that the apocalyptic fall occurred a long time ago, the Hiveguard are the last remaining vestige of a powerful civilization that once build the Hive.
Throughout time, lesser apocalypses have occurred (and continue to occur), as new incidents leave stranded souls in the complex. This means that there are numerous origins to the various communities, along with numerous technologies and cultural backgrounds.
When a group of adventurers explores the hive, they may encounter recent arrivals still possessing the degree of technology or magic that led them to the hive, they may encounter groups that have degraded slightly in their proficiency, or even tribal groups who have lost all technology and mystic insight.
When devising a settlement, it makes sense to define how the settlement might have started, and if this was due to the arrival of a specific group of survivors, it might be useful to determine what degree of technology or mystic power they had intially, and how far they might have fallen from this point. There are plenty of games that handle tech levels, but for simplicity I'll work with seven levels of technology and a few bonuses for psychic or magic potential in the culture.
0 - Stone Age
1 - Ancient Empires
2 - Dark Ages
3 - Rennaisance/Early Industrial
4 - Atomic Age
5 - Information Age
6 - Interplanetary Space Age
7 - Galactic/Transdimensional Exploration
0 - None
1 - Latent Psychics
2 - Instinctive Psychics
3 - Informally Trained Psychics
4 - Formal Psychic Colleges/Universities
0 - No Magic
1 - Limited Mystic Folklore
2 - Some Magical Apprenticeships
3 - Magical Guild System
4 - Common Magical Education
Add together the three categories, and if the total is 8 or greater, the civilization would be capable of reaching the Darkhive.
As some examples...
The Khar-Tui as a race of scholars would have originally reached a technology level where they plunged through the stars in transgalactic starships (tech 7), they would have navigated through astralspace/hyperspace by tapping into quantum mechanistic effects through psychic wayfarers (psychic 2).
The Riven as a race of warriors wouldn't have reached quite the same tech levels, scavenging technologies from others and honing their arms and armour to reach a limited level of industrial ingenuity (tech 3). The Riven have the advantage of being naturally psychic (psychic 4) and developing techniques of warfare dedicated to harnessing the mystic arts (magic 2).
The Ichthyans were enslaved as a part of the monstrous empire that was also responsible for the Shellbrood. As a part of this empire they had access to limited technologies enough for their station in society (tech 3), but they did have access to the psychic hivemind of the shellbrood's overmasters (psychic 3 and magic 3).
The same could be done for each of the races, or for any other race that you might want to introduce as a one-off faction in a settlement.
Next determine how much the innovation levels of the culture might have degraded. Generally across the hive, we assume a "Dark Ages" tech level (tech 2), with latent psychics (1) and magical superstitions (1). After a few years of survival in the Darkhive, a culture rolls 3d12 and allocate the results between tech, psy and magic. After an entire generation has lived in the hive, roll an extra d12 (and another die for every additional generation), then choose the lowest 3 results to allocate.
1-3: All advances made by this culture have been lost during their time in the hive.
4-7: The group has almost completely lost the innovations once known in this field by their culture (halve the innovation level, rounding up).
8-11: The group has lost the finer nuances of their culture's innovations (any levels formerly at 6 or higher are reduced by 2, any other levels are reduced by 1).
12: This particular group retains its original innovation level for their culture.
As I'm writing this...it's feeling a bit clunky mechanically, but it's got the right ideas that I'm aiming for. Maybe it needs a bit more thought.