As with all Bluetooth headphones, the range on these guys is about 30-40 feet, which means you can leave your phone or another Bluetooth-enabled audio device on the other side of the room, though most people will simply stow the phone in their pockets while wirelessly streaming audio.
As noted, you can also take calls using the headphones -- the microphone is built into the left earcup. I found call quality to be acceptable, though not great. I could hear callers well, but they said I sounded slightly muffled when I was walking outside on the streets of New York, where there was more ambient noise.
As for sound quality, it's OK. Depending on your frame of reference, the type of of headphones or earphones you normally wear, you may think it's just fine. However, if you're coming from a pair of decent wired headphones, you probably won't be so generous.
Bluetooth headphones have offered better performance in recent years, but my music over the Tenqa Remixd headphones felt a little stripped-down and lacked any sort of dynamic quality. There's a reasonable amount of bass but it's just not really punchy or vibrant (that's a polite way of saying it's a tad muddy).
You can look at the Tenqa Remxd Bluetooth headphones from a couple of angles. If you're comparing their sound with that of $40-$50 wired headphones (the Panasonic RP-HTX7 monitor headphones, for example), you're going to be disappointed. They just don't sound as dynamic or detailed.
But if you're someone who's on a very tight budget and wants Bluetooth headphones, they offer reasonable value for their $39 price. I have some quibbles about the design -- the headband won't fit smaller heads and I don't like the nonstandard USB charging cable -- but they sound OK for Bluetooth headphones and seem pretty sturdy.
If you're willing to spend about $25 more, you should check out the MEElectronics Air-Fi Runaway Bluetooth headset. I think the Air-Fis sound a bit better and fit slightly better, plus they have a fold-up design. I also like the LG Tone stereo Bluetooth headset (around $55). But that's an in-ear model, which some people don't like.