So, on Clan technical advancement: the vast majority of clan-grade military advancements happened during the Golden Century, at which point they started to stagnate and did not start advancing rapidly again until post-invasion. Their culture absolutely stifled scientific advancement, and is specifically called out in
Wars of Reaving. According to a clan scientist, the warriors ceased scientific inquiry into particle physics "because everything of worth has been discovered". IMO it indicates that a lot of their advancement was based on SL era research.
That said, this is an inaccurate view, however popular it is with clan haters:
No, instead, the Clans spent all that time under a fascist quasi-military dictatorship, culturally dominated by worship of the past
The clans are far more communist than fascist, leadership is not a dictatorship, and while there is immense respect for the founders it is not the central focus of their culture.
Clan culture abhors waste and living simply is considered virtuous, with minimal resources spent on luxury and thus minimizing wealth inequality. If anything, the ruling warrior caste's focus on honor/virtue means that luxuries are more likely to exist in the hands of the other castes.
Clan leadership is a strange hybrid of meritocratic chain-of-command with limited democracy and appeals through combat trials. Promotion is based primarily on ability (especially in other non-warrior castes), though trials may be held between equivalent candidates or between a leader and subordinate. The clan's council works by vote, though the electorate is generally limited to bloodnamed warriors. Among other things, the clan council elects the khans and sakhans, though those individuals can be challenged for their positions.
If anything defines the clans, it is survival of the fittest. Might makes right could also apply in military situations, and there tends to be a high degree of what could be described as nationalism in their culture. The founders are held in deep reverence and have a major influence in the culture, but its not like their culture is based on the worship of dead heroes.
I feel like a ton of the hate on clan culture looks at the Smoke Jaguars, who were authoritarian and violently repressive to their lower castes. They very much represent an outlier.