On one hand, you don't need to worry about too many specifications to figure out what you want; on the other, it helps to understand what you're looking at to prevent being blindsided by marketing claims. For instance, all webcams are plug-and-play, despite frequently being called out as a novelty, and claims like "DSLR-quality video" are meaningless. AI is not magic -- it doesn't automatically make a camera (or even a particular feature) better and the term is used excessively and very loosely in marketing. And your new external webcam won't necessarily be better than the one integrated into your laptop; integrated models increasingly are tuned to work with the operating systems in a way that third-party cameras aren't.
And improving your environment with good lighting or a better angle can frequently enhance the quality of your webcam video more than upgrading the camera itself. And even in an ideal environment, the best webcam won't necessarily deliver great video and audio quality on the other end -- that can depend on the consistency and quality of your network connection as well as the software you're using. Videoconferencing software, for example, tends to aggressively process the video for smoother and more consistent transmission over the network rather than looking great.
The webcams range from $20 to about $300, and the best models usually go for $200 and up. In general, price rises as resolution, features and quality gets better. There are some good 1080p models under $100, but if you want to save money on the admittedly pricey high-end models, you can frequently get the previous model at a good price and they tend to go on sale at the usual times of the year, like Black Friday season.
It's important to separate sensor resolution from video resolution; A lot of webcams with high resolutions (greater than 4K, which is equivalent to about 8 megapixels) don't actually produce video at it, instead using the extra pixels to get a better results when scaling down to the effective resolution of 1080p, 1440p or 4K, zooming and changing the field of view, low light performance, and more. That's why it's worth considering a 4K model to better frame yourself without looking soft, crunchy or blocky or to demonstrate physical objects.
But don't assume a camera with a high-resolution sensor can output video as, say, 4K. While all software supports 1080p (1,920x1,080 pixels, equivalent to 2 megapixels), other resolutions frequently require specific support -- notably by videoconferencing software. Zoom, for instance, maxes out at 1080p. Plus, keep in mind that software can take a good image and make it look... less good... by compressing the hell out of it for transmitting across the software's low-bandwidth pipeline.
Keep in mind that 4K and above webcams can generate a lot of heat, which might be an issue for you if you work in hot environments (prolonged heat may decrease image stability). The metal bodies may be sturdier and sometimes look more attractive, but they also draw heat away from the inside and get hotter to the touch than plastic.
And avoid 720p unless you're desperate and have no money. Even then, you can get a no-name 1080p model for about $20 (maybe less) that will at least be marginally better.
Field of view
Most webcams usually have a fixed field of view (which from your perspective is zoom or the amount of the view the lens covers); that's fine as long as it covers the amount you need. It's specified in degrees, typically in the range of about 65 degrees (narrow, covering roughly your head and shoulders) to 90 degrees (which can accommodate another person in the view). Conference room webcams tend to have much wider angle of views, unsurprisingly.
Webcams with that list multiple fields of view will frequently use digital zoom in order to achieve it, which means you want to go for a high-resolution webcam; it can look really bad when you start with a 1080p camera.
If the webcam has a wide FOV, then it will likely have distortion that makes straight vertical lines on the sides curve. If that will bother you, look for a narrower FOV, or for a webcam that uses multiple lens elements, which can combat distortion.
Not all webcams have built-in microphones; for instance, models targeted at streamers usually don't, since the assumption is you'll be using a high-quality headset or standalone mic instead of the webcam's. Built-in mics tend to be intended for everyday videoconferencing, and you rarely have any control over the characteristics of the sound.
But some are definitely better than others. Noise cancellation sometimes works well, but it often makes your voice sound a little (or a lot) processed, and you can't always control how aggressive it is. Many of the mics are omnidirectional, meaning they pick up sound from multiple locations, but that can generally be compensated for computationally.
Bottom line: If you care about sound quality and can tell good from bad, opt for a non-integrated mic or assume you'll need to supplement it with a dedicated mic. If you just want something "good enough," look at user reviews just to verify that a given webcam doesn't have relevant complaints about the mic.
These come in a billion different sizes and shapes, but the mounts -- the physical clip that lets you perch it on your screen -- are all very similar and tend to be stable but cumbersome. There's no "best" design, but if you want to use it on a laptop, you may want to avoid the big, clunky models.
One advantage bigger models have is the ability to remove the mounts or attach the mount itself to a tripod: Even a small tabletop tripod sitting behind your laptop screen can help avoid the weird looking-down angle you see with a lot of laptop webcams, by raising it to eye level. You'll probably still look down occasionally, but it feels more natural for the people on the other end.
The covers vary a lot, and the ones that completely detach and are fiddly to attach can be annoying and I lose them about 10 minutes after unboxing. But if you're tossing the webcam in a bag and carrying it around, you should definitely use something to protect the front.
Most of a webcam's features are only available via software. Almost any camera will work when you plug it into your USB-C or USB-A port (though 4K webcams frequently need a high-speed USB-C connection to get full resolution). And many of them work well this way. But I find some features essential, which are provided only by software: the ability to override exposure settings when they need correction; some small white balance control (auto usually delivers the best results, but I like to be able to make it slightly warmer or cooler); manual focus; and the ability to save the changes as presets. Presets are doubly important for cameras modeled off commercial PTZ (pan, tilt, zoom) webcams like the Obsbot and Insta360 models.
One thing to consider when buying a webcam for a Mac is that there are no controls built into the operating system and Windows doesn't really expose the settings (for good reason). If you want to adjust exposure, zoom, white balance -- anything really -- then the support needs to be built into the specific application or into a utility that comes with the camera. And autoexposure can be wrong at unexpected times.
All the cameras focus automatically, but unless you move around a lot, manual focus will let you set it and forget it, and even if you move a bit you don't have to deal with the webcam trying to lock onto you again. At best, it'll snap into focus after a slight delay; at worst, it will pulse unattractively searching for a focus lock. At its worst, it will fail to lock entirely. Although it's starting to change a bit on the higher end, webcams basically focus on the whole view.
Unfortunately, few manufacturers offer MacOS-compatible utilities; the Elgato FaceCam and FaceCam Pro and the Opal C1 and Tadpole are notable exceptions. The only settings you can control on the Mac natively aren't really intended for webcams -- Portrait mode (to blur the background) and Studio Lighting (to change the foreground/background exposure balance), neither of which works as well on the Mac as it does on an iPhone. And not all the software is as full-featured on both platforms, or maintained over time.
For Windows, consider whether you want to use Windows Hello for face recognition. Some external webcams support it, but not all; usually if a webcam supports it the manufacturer mentions it in the marketing materials.