Setting up the Audio-Technica ATH-CK3TW headphones is as simple as it is with most headphones of this type; take them out of their charging case and they'll start looking for suitable pairing partners. Search for them on your device of choice – in this day and age, almost always a smartphone – choose them and you're away. Nothing out of the ordinary here, and I encountered few issues with getting them to pair simply and quickly each time I wanted to use them.
If you've got a device that supports Qualcomm's TrueWireless Stereo Plus, it's supported by the Audio-Technica ATH-CK3TW headphones. That's still a relatively small list of phones to date, and to be clear, I rather deliberately tested with a phone that didn't support this to see how the Audio-Technica ATH-CK3TW headphones would stand up. Still, in theory, you should see even better pairing and battery life from a device with TrueWireless Stereo Plus on board.

The simple physical design of the Audio-Technica ATH-CK3TW headphones means that you're not looking at fancy features like active noise cancellation; the best you can hope for is simple noise isolation as the silicon tips fill out the space in your ears. That's always something of a mixed prospect with any bud headphones, but I was generally pleased with the Audio-Technica ATH-CK3TW headphones' sound output across a range of genres, at least relative to their price point.
Going the full cheese pop route, Taylor Swift's "ME!" displayed plenty of bright pop tones, but then most headphones can handle standard overproduced pop music fairly well. There's a slight bias in the Audio-Technica ATH-CK3TW headphones towards higher tones, but not one that's overly problematic for most music types.
Switching to something a tad heavier, "Godzilla", from the Godzilla: King Of The Monsters soundtrack, managed to present that track's grimier guitar lines with reasonable fidelity; it's a track where lesser headphones can reduce those tones to more of a muddy output, but the Audio-Technica ATH-CK3TW headphones managed well there.
Switching back a few decades, the piano tones in David Bowie's classic "Life On Mars" kept their proper reverb, although they did struggle a little with the more complex sound mix in The Who's "Won't Get Fooled Again". They didn't struggle to a terrible degree for buds at this price range, but it was one noticeable area where the Audio-Technica ATH-CK3TW headphones showed their preference for more high tones.

The Audio-Technica ATH-CK3TW headphones only feature a microphone on the right hand side bud, so I wasn't expecting great audio pick-up for calls in any case, especially as they lack any kind of external microphone array. I was pleasantly surprised with the few calls I made through them, with respondents indicating they could hear my voice quite clearly. However, there's an insane quantity of variance in voice calls that can depend on a lot more than microphone quality, so your experiences there may vary.
One feature of the Audio-Technica ATH-CK3TW headphones that I really didn't enjoy was the touch controls. They're simple enough in theory, with single, double or triple taps on the right bud to play/pause, skip forward or skip back and single and double taps on the left to raise and lower volume specifically.
However, they're something of a pain to use accurately. All too often, when I wanted to pause music, I'd end up skipping a track or pausing when I wanted to skip. It's noticeably more of a problem with the volume adjustment because the default tap is to adjust volume upwards, and I don't much enjoy being accidentally deafened when I'm seeking lower tones. It's also problematic for the double and triple taps on any ear because doing so always feels like you're deliberately trying to tap your own eardrum, which isn't that pleasant.