These seem to be the same as the iSK Little Gem and Lyxpro SDPC2. In my experience the iSK Little Gem was certainly quite noisy. Definitely over 20 dBA, but maybe it's inconsistent quality control, or maybe the Neewer is better quality for some reason. Glad to hear someone has a good experience with them though, almost makes me want to give the Neewer version a shot.
If anyone is wondering I never got any interference on mine, though I did only point them at a couple computers, my router and modem, cell phones, and anything else in my house that could cause interference. If you were to try to use these as spot mics for a play or something, or for a cheap backup mic for videography I'm sure there's a chance to pick up interference.
I will say that for the price the super cardioid had pretty good rejection from the quick tests I did. I don't recall comparing them to my MK-012s in that sense, though I did compare them (Little Gem version) on axis. No contest, but one is $50 with 3 capsules and one is $230 with one capsule.
I'd also love to see a measurement, since I don't trust the frequency response charts from iSK and Neewer.
In any case, I wouldn't recommend buying them individually from iSK given my experience, but the Neewer samples I've heard haven't been too bad. Usable at the very least and not as noisy. The electronics looked decent to my eyes, a bunch of film caps, I think there's a picture of the PCB in my iSK Little Gem thread.
This is a sample of them that is more or less what I experienced. Though I think my Little Gems were noisier
https://youtu.be/JWdkhkGafOI