This episode is a good example of why I love the character of Dax. There are so many possibilities for revisiting the symbiont’s previous lives and deciding what components make a person, and a personality. Jadzia is not Curzon, and Curzon was not Klingon, but she has a part to play in this story of Klingon honor and vengeance. It’s interesting.
Jadzia’s armor is closer to what we’ve seen before than the Old Guard Klingons, and it is possibly the simplest version we’ve seen since the Original Series. That works on multiple levels.
One: it calls back to the first appearances of these three Klingons (all were reprising their roles in TOS).
Two: it casts Jadzia as their D’Artagnan, and this her loss of innocence (that Jadzia is skilled in combat but has never participated in premeditated murder is a theme of the episode).
Three: relatedly, dressing her in a “blank slate” version of the armor while they are covered in the trappings of their station creates the impression that she is at the beginning of her Klingon journey while they are closing out the end of theirs (two die, meanwhile Jadzia flirts with being Klingon throughout the series, eventually marrying one).
And four: it looks more like a uniform than their furs and bling, which reminds us that she is a Starfleet officer and gives weight to her moral dilemma.
That sounds like a lot and you could argue I’m overthinking it, but this episode was set up to be scrutinized and costuming is an art form.
As for pure fashion, the under-suit is a pretty standard two tone woolen jumpusuit. But the jacket is a work of art. With slight modifications to the shoulders (it kinda looks like she’s gonna take flight in some of these shots), I would totally wear it over a dress to go clubbing.