I bought a Jinhao 85 when it was very recent (early corona days if I am not mistaken), and it was so good that I now I four of them in different colors, including one that I sanded down to paint myself to match my motorcycle (using the same paint). I love this pen and very much recommend it, it's very smooth, if a little (top) heavy for my taste, though nothing egregious. My oldest one (metallic blue with gold cap) has seen a lot of use, and for a while, became my main pen. I have never had an issue with it. The one thing that bothers me about it is that with the hooded nibs, the feed is glued in the section, so that limits the ink choices due to the inability to take it apart to clean it properly.
I am surprised that you were disappointed in Jinhao pens, at least recent ones, because I have 14 or 15 of them now, and not one of them has been a disappointment, though I know some of their older stuff is a little... dodgy to say the least. In contrast, Wing Sung and Hong Dian pens have never quite matched my expectations from reading online reviews.
There is also the Jinhao 911, lighter and slimmer, but same very smooth nibs. It feels a lot like writing with a pencil in terms of paper touch and feedback. I would also very much recommend this one, given the 2€ or so price point. Crazy good for the price, but does require extra care again, due to the hooded nib.
Do note that they both rely on (included) cartridge converters.
If the Jinhao 85 does look appealing to you in any way, and you can find it at a reasonable price where you live (I paid all of mine between 3 and 5€), please don't let the filling system hold you back, they are very good pens on their own, not just as a Parker 51 clone. And they manage to be a lot smoother with their steel nibs than the modern 51 with gold nibs, which I find disgraceful from Parker. Then again, their modern production is dismal.
I would consider the x750 middle of the road for Jinhao, not up to the quality of the more recent models (this one has been around for over a decade), but not awful. But their newer stuff is a LOT better. The exception is the 100, which I find to be a little lower quality than its contemporaries.
Hong Dian and Wing Sung, I have limited experience, 3 pens total, but too far from what I read online that I don't care to try any further. Not bad, but not good enough.
A lot of Chinese companies still stick to the old ways of no QC and replace when the customer is unhappy. This isn't specific to the pen world. Though for a lot of Chinese pen companies, there is also the fact that their newer designs are also intrinsically better, higher quality overall, but not necessarily with changes in QC, just better design and manufacturing. The only Chinese pen company I know to have very tight QC across the board is Pimio. Hero also has some good QC on some of their stuff, but they also have lousy QC on other pens.
Also, when buying Chinese pens, or anything Chinese really, I would very strongly advise to check AliExpress first, because they'll very likely be a LOT cheaper than Amazon. But even if they're closer in price, you'll often get a lot more choice in colorways, nib sizes, finishes, etc.