Having just finished the most recent Sword & Sorceress volume (and having read two earlier volumes in the past), I now have a fairly decent feel for the differences between the sensibilities of the subgenre versus the sensibilities of the anthology.
First, a tentative definition for sword and sorcery: a secondary world fantasy story with a focus on adventure and combat, where magic is either "the enemy," limited or capricious, with a lower technology level and personal stakes. There are caveats to these pointers - the Gray Mouser has magical training; Conan, after all, becomes a king - but these are central points of the subgenre.
Here is how Sword & Sorceress compares:
Secondary world: Check (though there is one contemporary story in XXIV)
Adventure and combat: Half a check. There's a lot of adventure and action in the anthologies, but not necessarily all of it has to do with fighting or spell-slinging. I mentioned in my review above that the primary action in one story is a foot race. And a small number of the stories have external goals but no "adventure" thread.
Use of magic: This is one of the most noticeable differences - Sword & Sorceress features a number of characters who make use of magic, are born of mystical origins, or make pacts with beings for sorcerous powers. Where it does prominently align with the sword and sorcery theme, however, is the fact that the magic is mysterious. When it's a tool in the hands of the main character(s), it's never fully understood or fully under control.
Lower technology level: Check (with a few exceptions)
Personal stakes: This is the other place where Sword & Sorceress differs. There are a number of queens and ladies fighting to defend their territory, and / or where the fate of an entire kingdom is threatened. Some (but not all) of these stories give the personal stakes of the character equal weight.
So in sum, a sword and sorcery story would generally fit well with the Sword & Sorceress anthology series, but a story suited to Sword & Sorceress is not necessarily a traditional sword and sorcery story.
I enter the fray feeling better about my story selections. I have four that I'm preparing - yes, four. There are three reasons for this. First off, I know from previous experience that they reject stories within a few days, with the exception of those held for the final cut. Second off, my previous history has been that I usually don't get a "hold" on the first story. It could certainly happen, but I don't want to give up if that's the case. Third off, while my editing skills continue to improve, I still don't seem to have dead-on accuracy for what my best story is - so best to have a few options.
So my current roster, as lined up to send, rounded to the nearest five hundred words:
Just The Messenger / Her Father's Daughter (9k): Thorn is a Scion of Whispers - a messenger whose route takes her through the perilous shadow realms - tasked with a message she will only learn when she reaches her destination. When elderly healer Squirrel invites himself along, Thorn finds an unexpected ally against the perils of the ride. (I haven't definitely settled on the title here, ergo the slash.)
A Flattering Likeness (9k): Anaphys is a painter without peer, using mystical paints derived from the essence of his subjects. The mysterious mercenary woman Aura bails him out of an attack by an irate monarch, and the pair strike out in search of a way to make amends. (This one needs a bit more editing for at least one reason: it's currently over the 9k limit.)
Bird Out of Water (7k): Vri is the child of a harpy / merman romance - awkward, isolated, believing herself a monster. When the tantalizing offer of escape - the chance to become human - turns into betrayal and imprisonment as the latest attraction of a zoo, Vri must decide what she really wants.
Saplings (5k): Once an herbalist, Hevia found herself burdened with childminding powers and a position as royal nanny. But of all her charges, why do mysterious tree-spirits abduct the son of a gardener?
I think I'm fairly well-calibrated with the Sword & Sorceress lens, but whether any of the stories are good enough to pass (especially since they're all in the upper word counts) is another story. We'll see!