So the NiceHCK NX7 mk IV finally arrived this morning. I've had about two hours of listening time with them. They come with three tuning screws. Gold, Black, and Red.
I started listening with stock cable (NiceHCK always includes a quality cable in their IEM's, so I rarely feel the need to cable roll), Spiral Dot tips, and DX170 DAP (The NX7 series never required an amp to drive and it doesn't necessarily scale all that noticeably with an amp).
With the gold screw, the apparent weaknesses of the previous versions have been tweaked and "improved" upon.
@Surf Monkey touched on these in his observations. So the mids are fuller, the mid bass is most definitely lifted, and the signature is mostly harmanish with slightly recessed mids, bass thump, and reigned in treble (the air ain't there, but the stage has been widened. The piezo's are slightly tamed), with the bass and mid bass in particular allowed to flourish. The thin mids are all gone, but the mids have been pulled back some, like the earliest NX7 models. So those who like bouncy bass (still not much sub bass, so don't get excited about that), and a warm hamanish tuning, the gold screws will please you. Here's my observation about this. In the price bracket these belong to, there's just some stiff competition. The Zetian Wu sits in this bracket, and frankly, there aren't as good as the Wu, and the Wu's sound more upscale, just with less bass. The problem is that yes, NiceHCK worked on some of the complaints of earlier models, and fixed it in the tuning, EXCEPT imaging. The imaging is still very linear, and lacks depth. It's a very detailed and bass responsive sound with wider stage, but very 2D imaging. Had they taken the time to work on a more 3D stage and presentation, then we could say they matured the sound beyond it's price range. It would be a standout. But the dimensional presentation is exactly the SAME as the previous iteration. So instead of separating itself from the pack and bringing in new listeners, they will basically just get those who already own the previous version, as an upgrade on THAT. It's not an upgrade in the price bracket, where legends are made as well as money $$$$. It's a really good tribrid in the $100-150 price bracket, that will be really good for metal and hard rock fans, but for other genres, there's better options in the bracket.
I switched to the black screws, and this freed up the trebles, as well as added a bit more air up top. It also improved the timber a bit to my ears, as the highs are allowed to ring truer and longer than the more refined and reserved gold screw. It reminded me of the MK III, just with a little more stage. They still need burn in time, and to be broken in, because the mk III bass is much more refined and quicker doing an A-B, but that's because my mk III are beyond broken in. They are well worn. I'll be settling in with the black tips, as i'm just not a fan of Harman tuning in the treble region, and the red screws are bassy and designed for those who delight in a deeper, more bass excited presentation. Still, don't expect too much sub bass here either. The double dynamic drivers of the mk III and mk IV are tuned to work in tandem to provide incredible speed and punch to the sound and not so much one working on bass and the other on sub bass. Now it's there when sub bass is called upon, but it's not ever present or hitting low sub bass floors like the Salnotes Zero.
So i'll continue to listen to them after work and after some more burn in time, and then i'll check in with any further changes or refinements as we go along. OOTB rating? B. I like them. I enjoy them, but with some caveats mentioned above. So far a solid B rating.
Oh by the way, the stabilized wood face plates are BEAUTIFUL, but the shape and size of the shell are identical to the mk III, just substituting a metal removeable face plate for one that's stabilized wood.
of the IEM world. At the time, my knee jerk reaction was to think: good for you buddy, now please move on. But as I’ve spent more time (and more $$$ than I should’ve), I can accept that KZ is the Pinto; but I respect them for staying in their lane (<$75) and continue to offer new solutions. Some real and some with smoke and mirrors 
