While I would say that the submarine construction program has been abysmal relative to the surface program (excluding the new massive sub construction base), the technology development seems on point and even accelerating with some cutting edge tech introduced.
The surface ship construction program also had its difficulties. You have the Type 052 which was revolutionary for China as it was the first blue ocean destroyer with gas turbines they made. But it had terrible weapons and sensors integration. It was all over the place. China then had its access to the LM2500 turbines cut off. They made the Type 051B because of this. It went a step back and switched to steam turbines. While China in the meantime managed to make their own integrated combat system and reverse engineered some systems like the short range SAMs in the Type 052 and some of the sensors, both sensors and weapons were obsolete. So they imported the Sovremennyy destroyers from Russia. At the same time they reverse engineered Ukrainian naval gas turbines. They reverse engineered sensors and weapon systems from the Sovremennyy destroyers. The result is the Type 052B. This was the successful integration of all those technologies and is basically what the original Type 052 should have been. You get the Type 051C which is another steam turbine powered ship which is larger in displacement than the 052s thus far that has heavier SAMs like the ones on Soviet cruisers. Then you start seeing expansions of the Type 052B with more modern Chinese sensors, enlarged ship hulls, UVLS, and you get to the Type 052C/D.
This took a couple of decades to happen. Now if you look at the submarines the process is much different. China could basically either have made a sort of Type 052 equivalent where they mishmash all available technology together and use those boats as test beds. Or they can try to improve their available submarines in a more iterative fashion. Or they could have bought boats from other countries.
So you have the Type 039 which is basically an integration of West European submarine technology. I suppose you could call this the equivalent of the Type 052 in terms of conventional submarines but the integration was more successful. Then they bought the Kilo from Russia. They reverse engineered the Club-S cruise missile they got with the Kilo. They made a larger conventional submarine, the Type 039A and put those cruise missiles in it. So this would be a sort of Type 052B equivalent I guess.
With regards to the nuclear submarines, the development is a lot more complicated. China basically had no technology transfer and had to do their first nuclear submarine by themselves as the Type 091. They basically copied the hull design from a US nuclear submarine then put the rest of the components the best they could. The Type 093 is supposed to be an extended hull version of the Type 091. But to be honest available information on this submarine is quite limited. Like we don't even know precisely which reactor it uses. What we do know is that back when they started development of this the first Chinese civilian LWRs with modern Western reactor technology were just being started up. Which weapons it uses is also, frankly, kind of unknown and mostly speculation. What we do know is they have been improving the hull shape and improving quieting technologies in later types. This is likely an infusion of technology from the conventional submarine program I think. The later batches which are dubbed the Type 093G. These I suspect have a new nuclear reactor type. I say this because if you look at the civilian nuclear program then it makes sense they would upgrade the reactor design at this point. This is about the time China started making their own civilian reactor designs.
