I agree with everyone that the possibility of Matter is upending device choices at the moment. Matter promises to make integrating different brands a LOT easier and it’s promoting widespread adoption of Thread, a mesh protocol similar in some ways to Zigbee and zwave, but with IPv6 support. Only SmartThings doesn’t currently support Thread (but should support Matter-compliant Thread devices eventually). So…complicated. 
Here are some choices to consider, but different ones will work for different people.
- the most futureproof choice in this “Matter is coming” moment: Lutron Caseta with a Lutron Caseta SmartBridge Pro for integration.
Really well engineered, Matter support is promised, offers SmartThings integration which is decent but with occasional glitches. Does not require a SmartThings hub. I use these in my own home. Available in lots of colors.
The biggest negative is the cost, which is usually $60 for a single dimmer switch, or $70 for a 3 way kit with one master dimmer switch and one battery powered auxiliary switch. Plus the bridge, which lists around $150 for the pro version and can handle up to 75 individual Lutron devices. These rarely go on sale, although if you’re buying at least 10 you may be able to get a small discount at the Home Depot contractor desk.
The Caseta switch, Caseta dimmer switch, Caseta fan switch, and Serena smart shades work with SmartThings. The motion sensor and other model devices do not at present, although more may once Matter support is added to both platforms. The battery powered Pico auxiliary switch will work fine with its own Master switch in a 3 way, but you can’t use it for anything else with SmartThings through the official integration. (Works great with Hubitat, though.)
As @ogiewon notes below, each SmartBridge can handle up to 75 Lutron devices.
My personal favorite switches for a bunch of technical engineering reasons, but costly.
https://www.amazon.com/Lutron-Wireless-Lighting-P-PKG1W-WH-Assistant/dp/B00JJY0S4G
- Best current (March 2022) SmartThings integration is probably Zooz or Inovelli Zwave switches with a SmartThings hub, and both also happen to be moderately priced at about half the cost of a Lutron dimmer switch. Both are small companies which are fully committed to keeping up with SmartThings platform changes, of which we can expect to see a lot over the next few years. Both are taking full advantage of zwave advanced features.
Zooz is the house brand of The Smartest House retailer and has done a better job of handling supply chain disruptions over the last 2 years, but otherwise both companies have excellent customer support and an active presence in this forum. Both run occasional sales making good prices very good. Both may offer a small volume discount if you write and ask.
But…zwave itself is not yet onboard with Matter. And as @Automated_House noted, the new SmartThings dongles for their tv’s are only going to have Zigbee, no zwave. So there is some question about Samsung’s long term commitment to nonMatter technologies…
https://www.thesmartesthouse.com/collections/zooz
- Best nonLutron compatibility with Matter. Hmmm….probably Thread, but only one company, Eve, has so far announced a Thread light switch, and it doesn’t yet work with SmartThings at all. So
I mention it only for completeness, but personally I’d wait before buying these until they work with SmartThings directly.
- Best WiFi switch that currently works with SmartThings. Meross, which is very inexpensive, probably has the best current ST integration for an all in one design using WiFi. good safety certifications. They haven’t announced support for Matter yet, but will probably get there eventually because they already have a HomeKit version. Great prices, and they usually offer bundle packs at a discount.
https://www.amazon.com/meross-Supports-Assistant-SmartThings-Dimmable/dp/B08GPBH5NK/
There are some other brands to consider, including the Sonoff inline modules, so hopefully you will get other recommendations in this category.
Also, Matter might bring in a lot of New Wi-Fi candidates, but who knows when? Just as an example, Leviton had smartthings integration for their first generation Wi-Fi switch, but then dropped it for the second generation so that now you have to use Ifttt for those. But they are likely to have matter support in the future, which then would bring those back in once SmartThings also has matter support. So it’s hard to project what will be a good choice in the WiFi category for a year from now.
The WiFi router issue that @HalD mentioned is that different WiFi routers have different limits on how many WiFi devices can be attached at once, with some as low as 32 and many at around 50. 
However almost all of the gig speed routers have significantly increased this limit, most to at least 150, some as high as 250, so it’s less of an issue than it used to be. Still something to be aware of.
Also a WiFi device probably uses about 3 times as much power as a zwave, Zigbee, thread, or Lutron device, even when it’s “off.” Although that’s a big issue for battery powered devices, the total $ cost to operate the radio for a mains powered WiFi smart plug, for example, is still probably under $10/year, so you may not care about the extra cost vs other protocols unless, like me, your house runs on solar and you count every watt saved as a plus. 
- That brings us to Zigbee. Which weirdly probably has the most unknowns right now, although as a protocol it’s older than both zwave and Thread.
On the plus side, SmartThings did include it in those dongles, some models do work well with SmartThings right now, and it’s involved in Matter although no individual devices have announced Matter support yet except via a bridge because Zigbee itself doesn’t use IP addresses.
On the negative side, there are issues for multi gang devices with the new Edge architecture and voice assistants, there are some manufacturer-specific options that make shopping a bear, WiFi can still drown it out (probably why zwave has historically been more popular for low cost DIY install light switches), and a lot of brands don’t have the same safety certifications as the popular Lutron, zwave and WiFi brands, probably to keep costs as low as possible.
Historically Lutron has competed on precision (and usually patented) engineering, Zwave has competed on features, WiFi has competed on perceived simplicity, and Zigbee has competed on price.
As far as Zigbee brands…Inovelli has indicated they will be bringing out a new Zigbee line pretty soon, that will be worth looking at. GE by Jasco is probably the safest choice right now, with good ST compatibility and reasonable safety certifications. Only the GE line have tended to be expensive for Zigbee unless you can get them through a contractor channel.
https://www.amazon.com/GE-Lighting-Compatible-Monitoring-45857GE/dp/B015YJAHY0/
Leviton makes a nice Zigbee line, but I don’t know if it works with ST now. And like the GE, it’s way more expensive than most Zigbee brands.
I would personally avoid anything Zigbee from Tuya, they have that manufacturer-proprietary issue, as do the newest Aqara models.
Bottomline: you can find dozens of super cheap Zigbee switches but a lot of them won’t work with smartthings out of the box and many don’t have good safety certifications.
- BONUS OPTION: NO BATTERY, NO WIRING WALL SWITCH FOR CONTROLLING SCENES OR OTHER SMART DEVICES (REQUIRES HUE BRIDGE)
I really really like the EnOcean Zigbee battery free switches that work with HomeKit via a Hue bridge and have several, but they don’t work with ST, so not a candidate for your scenario unless you just want a parallel means of control. But amazing engineering. (HomeKit gives you even more features, but they work just fine with the android version of the Hue app, although again no ST integration except as a parallel means of control.) $79, but it’s a two gang switch.
Anyway, if you have a Hue bridge and you have a place where you just want to put a switch on the wall to control other devices connected to that Hue bridge (or HomeKit), this is a worthy candidate. For example, this is a great switch for manual control of outdoor LED strips connected to a Hue bridge. 
https://www.amazon.com/Senic-Compatible-Batteries-Charging-Wireless/dp/B08HXWLJWR/
SUMMARY
Well, those are some of the protocol specifics, but I don’t know if it really helps. As others have mentioned, the whole industry is in flux right now waiting to see what will happen with matter support.
Personally, if I had to buy a bunch of light switches in the next few months, I’d get Lutron Caseta, but that’s just me. It would probably cost an extra $15 - $30 per switch, but it would be responsive, reliable, works with a lot of different platforms including probably the future Matter, is UL listed for safety, has great engineering, comes in several colors, doesn’t require the ST hub, and is widely available including at Home Depot. But other people might choose something else. Choice is good.