These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Draka
Complete Monster: Louis Gayner. A female human Draka with a completely Alien morality enough to give Eric Von Shrakenberg the willies. To sum it up, she plans to remove sapiency from serfs and make them "organic machinery, nothing else", is pissed when serfs even talk around her, treat them as things (remember Silence of the Lambs?). To top that, in an all female boarding school, she is the ultimate heterosexual woman with no plans for reproduction, but skilled in genetics and planned the "New Race" project. Whom she cannot persuade, she duels to prove her point. So she singlehandedly represents all that is evil in Draka.
Family-Unfriendly Aesop: The Draka are the descendants of American loyalists, French noblemen and Confederates who lost the war / Revolution. Leading to the aesop: The revenge of losers will be horrible.
Looking at the Draka philosophy, it reads very much like the AnviliciousWW2-Allied propaganda version of what Nazi/Imperial Japanese ideology was supposedly like. Specifically, "Elvira Naldorssen" on the Quotes page copies lines the now-discredited "black propaganda" book The Voice of Destruction attributes to Hitler almost word for word. Combine this with the Draka fielding at least some of the sci-fi weaponry the real-life Nazis didn't have, but usually got in the pulp stories of the day. If this isn't just a coincidence, it's high-order Fridge Brilliance: Stirling is comparing and contrasting more-or-less realistic Nazis with the highly exaggerated propaganda image of Nazis in pop culture by having them fight against each other!
Nightmare Fuel: The Draka refine this in large quantities. You know it's bad when they make the Nazis appear tame in comparison you ROOT for the Nazis when they face off against the Draka.
In Marching Through Georgia Standartenfuhrer Felix Hoth, a fanatic Nazi war criminal who was canonically a rapist and mass murderer, still tempts the reader to root for him because at least he's not the Draka.
There's a line early in Marching Through Georgia that states that even the Draka high command were shaken by reports of the Nazi death camps. But from what we see of the Draka, that's hard to believe.
They weren't shocked by the moral dimension of it, they were shocked at the waste of valuable resources. It's so typically Draka that when confronted with the Holocaust, their emotional reaction is 'But you could have used them for something!'
To be the Devil's advocate, they don't like unnecessary torture to their serfs either. If they targeted a population for extermination, the Draka wouldn't bother with slow abuse, but simply go in and kill hand-to-hand. Or with machine guns. Or mortars. Or bombs. Or nerve gas... let's just say the Draka are very utilarian and leave it at that.
The middle book, Under the Yoke., which includes descriptions of how Draka treat slaves.
A Human Empire with an alien morality invades Europe and the rest of the world, reduces everyone into Roman style slaves, serf women can be raped anytime and are regularly raped, and every last LaResistance is prevented by massacres on spot, and after World War 3, the serfs are genetically modified to accept slavery meekly, and despise "ferals", humans who resist the Draka. Every effort of human resistance is forever forgotten on Earth.
With nothing more than strategic autarky, nuclear weapons and a global reach, and a tech advancement rate identical to our own, and the Draka would *never* fall. Unlike the Soviet Union, there was never any pretense of equality and for the masses it never mattered if the outside world had a better standard of living. Don't believe me? Look at North Korea. They do not have strategic autarky, their nuclear deterrent is laughable, possibly non-existent, and could be crushed and annihilated in a historical instant. Had OTL South Africa had a nuclear deterrent of the French scale by 1979, Aparthied might still be going on.
Uncanny Valley: Stirling went to great length into suggesting the alienness / otherness of the Draka in everything pertaining to their social life, until they could just as well be some extraterrestrial beings. In Under The Yoke, some contrasts between Draka and Frenchmen or Finns are obviously deliberate:
Language: Tanya von Shrakenberg talks (especially about sex) almost exactly like a young male from Real Life, although with no rough words. Funnily, males (even Draka) are more conservative in their language, more typical to a Real Life man from the 1940s.
Body Language: the Draka are not called 'snakes' in order to make an Incredibly Lame Pun. They practice extreme conservation of body movement, making no gesture or expression that is not completely intended and betraying nothing with their mannerisms. The effect on Alliance citizens who interact with the Draka is described as extremely unsettling.
Architecture: Draka buildings are so colorful and pimped-out they might just as well be from a fairy tale. European designs of the time were exactly the opposite, neat, clean, marble everywhere, or older gray masonry.
Clothing: also colorful and tacky for civilians, almost BDSM for troopers. Real Life fashions of the time (to fit the rather polluted European and American cities and muddy countryside) used strong fabrics, dull colors, rougher designs - unlike what a modern person may believe, Film Noir characters wore their coats and suits for practical reasons.
Staging: Draka use the parades and other public events in a disconcerting manner, like some 20th century Ancient Romans or Ancient Persians. By comparison, Third Reich public events were conceived to impress foreign observers and prove the strength of the regime. Draka public events were designed by Draka for Draka, nobody cared what someone else may understand (or if someone else understand them or not at all).
Attitude: the Nazis in Real Life looked and talked like a military aggressor was supposed to: they occupied land, settled themselves, captured supplies and production facilities, interrogated prisoners; there was a language in which people could relate to them. The Draka thought like a different species, they did not show any interest in European cities, edifices, art and other valuables, just molded the landscape immediately to fit them.
The Draka did appreciate fine art, especially Greco-Roman and Renaissance work. They systematically looted the Vatican specifically for its art collection.
Villain Sue: Several readers have noted multiple instances of Idiot Ball acting in the favor of the Draka during their rise to power; as mentioned above, much of the point of the Draka is to have The Empirewin "for a change". Still it's somewhat unlikely and Stirling shows complete favoritism.
One review of the Wraeththu RPG described the Draka books as "handing them an I Win button."
Stirling in later years has become more willing to acknowledge the holes in his earlier work (the Draka series was one of his first professional sales). In the Drakas! anthology (which he edited) there is a rather ruthless deconstruction by another author of Marching Through Georgia in general and Eric von Shrakenberg in particular. One of the best stories in the book.
However, that's what you get with alternate-universe fiction. Those many, many universes in which the Draka much more plausibly got their asses handed to them aren't the ones we end up hearing about.
There have been quite a few attempts essayed, some more successful than others, to write alternates to the Alternate Universe in which the Draka get theirs. Alternatehistory.com, as noted above, plays host to a number of them. Stirling himself participated in forum discussions related to several of those writing projects: There was least one incident in which Stirling got into a tremendous fight with several participants in one of those projects about just how absurdly over-armored the Draka Rhino ground-attack aircraft was.
Admittedly, the A-10 "Warthog" is almost that absurdly armored in real life.