What I'm thinking now is that Augen could have started off as an apprentice metalsmith, which would be a source of pride in their kingdom as a famous or remarkable industry—but that, the workflow simply didn't suit him. He could have this cooperative mindset of how if so many people in his neighborhood are metalsmiths then he doesn't have to be one more, especially if he doesn't want to stay indoors leaning over red-hot ingots every day. I imagine that the commission requests might have gone more towards "hearth-toaster" or "steel grater/mandolin" and not only weapons, which loosened up his consciousness towards how steel is really only a tool: it can be a weapon, or it can be kitchenware (or, I dunno, clockwork pieces… I don't know your world's technology level.) Then it wasn't like some latent desire to go to war is in every hammer-blow
So if he signed up to be on the city patrol, especially during a time of peace, then he could walk around and check in on people, more than raring at the bit for a fight.
I might suggest, then, for Augen the character trait of good-natured nosiness. If he's had to break up a bar brawl, he could find it a necessary effort to keep the peace, and find that he's successful to that end.
But it really all depends on what will move your story forward in a way that's interesting to you. If it's more interesting to you that Augen is cynical and bitter and has a mysterious past because he comes from another kingdom, or that his only consolation is the salary he drinks away to block his post-traumatic stress and the uniform finery he gets from serving a prestigious family…or something like that…or if he's been raised at a monastery, or was "the spare heir" of a family of lower nobility, recommended transfer to the royal guard because he's naturally tall and muscular, and/or has a romantic subplot with the princess' tutor or a housekeeper or lady-in-waiting…then, that's what it's going to be.
I can headcanon Augen as having working-class roots, but really any trait you decide on can then be compared or contrasted with Kaffer to define Kaffer's character too: Would it be more interesting to you for the purpose of the story if Kaffer were working-class, or gentry, or nobility? How well-traveled or well-educated would Kaffer or Augen be compared to one another? Where does their loyalty come from—Have royal decrees worked in their favor, and/or does the king or princess remind them of a younger sister or a good friend from their past? Or even the queen reminding them of a spoiled yet sternly overprotective and emotionally unstable aunt?
Finally: At what plot points will these traits matter? Are they supposed to make these characters sympathetic to the reader right before they die? Or are there skills you need to pull out of a character to make something in the plot happen?
For the latter, it's like…if Augen is A People Person, and rumors start going around that "the queen has gone mad", then Augen can quell any rebellion just by talking, which wouldn't work if he were seen as a standoffish class traitor instead of "yeah, that's Papa Augen, he was on the beat in our neighborhood when I was a wee child, we all know him so if he says the queen is just sad about the princess like any ordinary mother would be then it must be true."
So if Kaffer is an overgrown sheltered/spoiled child who's only read history books about strategizing war, or if he's somebody street-savvy and underhanded without much brute physical strength or weapons finesse, then that's going to change how he deals with plot happening to him as opposed to if he were a bland faceless background character…which you can still do, if their personalities aren't going to be important to the whole story anyway.
