Filters
Modern is a set of decisions, not a look
Almost any sconce could be called modern in a listing, so the word does no work on its own. What it actually describes is a group of choices the maker committed to, and each turns up in the specification.
Four forms come up again and again: a bar, a disc, a cylinder, a flat panel. No molding, no scrollwork, no candle tube. That has a consequence worth knowing before you buy. A traditional sconce can have ordinary proportions and still look good, because the detail carries it. A modern one has nothing to fall back on. The shape and the finish are the whole design, which is why two sconces of the same form at the same price can land very differently on a wall.
The bulb went away
Some of what is here takes a replaceable bulb, and only some of those arrive with one in the box. In the rest the LED is built into the fixture.
That is the largest single difference between a modern sconce and an older one, and it cuts both ways. A built-in LED lets the body get thin. A lit bar 1.7 in (4.5 cm) wide has nowhere to put a bulb. It also means the light color and the brightness were settled at the factory rather than in a shop, so the specification is the product. And when the LED eventually goes, the fixture goes with it. There is nothing to unscrew.
The switch left the wall
Many of these have a touch sensor on the fixture itself, and a good number come with a remote. The rest use the older arrangement: an inline switch on the cord, a push switch on the body, or the wall switch the circuit is wired to.
The first group is the reason a modern sconce can go on a wall with no switch and no socket. It is also worth a thought about how it gets used. A touch sensor is quick if you can reach the fixture and no use at all from across the room, which is what the remotes are for.
One design hides the control completely: a marble disc with a metal center you tap. Nothing in the photograph tells you that center is the switch.
The decoration moved into the material
Some of these are stone or ceramic, travertine, marble, microcement, glazed ceramic. Others use wood. The finishes on the rest stay narrow: black, brass or gold, white, nickel, bronze, chrome.
This is how a modern fixture earns its interest without ornament. The grain in a walnut disc and the pitting in a travertine panel do the job a cast detail used to do. It also means no two pieces are identical, and the product pages say so: natural stone varies in veining and tone, and a wood finish varies with the board it came from. If you want a matching pair either side of a bed, treat that variation as the thing to expect rather than the thing to query.
The backplate is smaller than you think
Modern backplates are small on purpose. A round disc of about 3.9 in (10 cm) is common here, as is a slim oblong of roughly 4.7 in by 2.0 in (12 cm by 5 cm).
That matters in one specific case: replacing an older fixture. Older sconces often sat on a wide plate, and after a few years the wall around it is a different color to the wall under it. A small modern plate will not cover that outline. Measure what is up there now before you order, because the remedy is paint, not a bigger sconce.
Three light colors, or one
Many of these switch between light colors on the fixture, usually warm 3000K, neutral 4000K and cool 6000K out of the same unit. A few let you pick warm or cool when you order, which is not the same thing; that choice is made once and then it is fixed.
Others are fixed warm, usually 3000K, and that is not a lesser specification. A bedroom or a living room wants warm light all evening and never wants anything else, and a fixture with one setting cannot be left on the wrong one. On the ones that take a bulb you are not picking a setting at all. You are picking a bulb.
Modern does not mean wired in
Many of these run on a battery, nearly all of those recharging from a USB cable. Others plug into an outlet, and the rest are hardwired.
So the style question and the wiring question are separate here, and neither has to be traded for the other. Narrow by whichever one matters more to you and there is still a shelf of sconces left.
Two things to check before you order
Whether the light color is switchable or fixed, and if it is fixed, whether the fixed one is right for the room it is going in.
The backplate, against whatever is on the wall now. That is the detail that turns a good sconce into a weekend of painting.