This class just feels like a test-bed; a test-bed for new sensors and the improved new variant CODAD power plants.
They didn't bothered with any significant weapons upgrades compared to the 054A. They also didn't bother on aesthetically redesigning the main gun and instead stuck the old HPJ-87 100mm gun on them.
They are testing things out--power plant and sensors--with these two before moving on to the real next FFG.
One thing for sure though, they are forecasting what they want their next FFG to be; a ship capable of housing a Z-20F. This logical means an increase in size from the 054A which also means a newer CODAD to handle the increase in tonnage and the new power requirements for the new sensors.
Who knows where they move on from 054B but I think these two are one off.
None of these techs are however, disruptive and tech breaking. This isn't like the Type 052C the first two came in 2004, and just how many ships then have large AESA radars.
The first two 052C were like proving and debugging ships, and after all the problems were detected and sorted out, they gave approval to finish the last four ships with refinements added from the experience of the two ships. The first two 052D were also proving and debugging ships, and once issues were sorted out, the rest of the line were approved albeit with improvements and refinements addressing discovered issues.
The 052, 051B, 051C and 052B were more like failures for a whole bunch of issues like not performing well enough, specs that are sufficiently capable and got obsolete quickly, lack of long term potential and dependence on foreign parts. So they got axed on the vine and the PLAN moved on.
The pair of 054 were the intros to the entire line. They decided from the experience the ships lack enough combat potential and that led to the 054A. However the techs on the 054A were conservative and derivative, one might say it's also takes techs off the 052B and the Project 956. Nonetheless the first four 054A acted like proving and debugging ships.
The first pair of 054B are proving and debugging ships. Test beds are for testing individual new technologies. But other ships have already done that, namely the purposely made radar and weapons testing ships. These new 054B is testing and debugging out issues as a new class, the lessons of which will be applied to the next ships.