Well, first of all, envision a wall. It looks like someone threw paintballs at it, and they splattered. It's not. It's a plotting of various stories according their types. Any one of those apparent paintballs, where the stories clump so thickly you can't tell them apart, is a genre. And where exactly you draw the circle about the splotch, and how much the points have to have thinned about before you draw that line, determines what you consider in the genre among the border-line cases.
Me, I'm thinking about the dead center of it, where you can't tell one story from the next because they are so thick on the wall.
(And how do we manage to reduce all the dimensions of genre to two, so that it fits on a wall? Talent, my boy, talent!)
And comparing it to epic fantasy, its closest competitor for many borderline cases. Both of them take place in high-magic worlds, with wizards and dragons and their ilk, although epics tend to be imaginary or impossibly far off in time, and sword and sorcery, while it can happen there, can also happen in loose approximations of history. (Obviously -- we'd have noticed the War of the Ring, but some sword and sorcery can slip around the corners of history. But if you start getting real historical figures, geography, or events in your sword and sorcery, you have slipped off the center, even if you still fall into the genre.) The sword-and-sorcery worlds tend to be grittier, too.
The characters are more obvious. Starting with the threats they face. The epic fantasy hero is out to save the world, with personal benefits as a sideline; the sword-and-sorcery hero is out to benefit himself (though it doesn't have to be anything wrong that he's seeking), and any good deeds are possible but incidental to that. Which is why the moral compass tends to be fuzzier on sword-and-sorcery. The epic hero tends to be younger than the sword-and-sorcery one, and this tends to his sole adventure, unlike the endless series of sword and sorcery -- partly because world-threatening perils are rarer than the personal problems, and partly because the sword-and-sorcery hero is the one who's an adrenaline junkie.
There's borderline cases, of course. Andre Norton's Witch World is heavy on epic-fantasy-type heroes facing sword-and-sorcery scale problems. And gritty epic fantasy can drift toward sword-and-sorcery.
But I was pondering what sorts of settings a sword-and-sorcery story could get into. Steampunk? Nah, not unless it was the pseudo-magical tech of a lost era. Swordsmen existed in the Victorian era, but for duels and ceremonial usages -- the German students who wanted to get dueling scars -- and I can't see Conan, even from a less civilized part of the world, sticking to his sword for reasons of honor when other men had guns.
Then, the Ruritarian romances featured swordplay. And lots of it. And the steampunk world, like the Victorian, would involve a lot more travel because travel was a lot more easy. Out to the Balkans, say, still notorious for their feuding at the time (and in places, now). Swords and daggers as well as guns -- and if you ranged farther afield, there might be a time between transportation reaching it and guns being standard issue. . . .
You could do something closely related to sword & sorcery, but I suspect that the steampunk elements would give sword & steam a different flavor.