So if these rumours are true, that means the main difference between the 054A and 054B would be propulsion and weapons.
From the above, my guess is that the 054B will probably be more of a proof-of-concept, transitional, small production run class, similar to the 052B and original 054 classes, rather than be another mainstream 054A class.
In terms of weapons, the biggest change would be to replace the current VLS with the new universal VLS (uVLS), and may serve as a proof of concept design to allow the eventual retrofitting of the uVLS onto the existing 054A fleet (hence the rationale for keeping the tonnage and dimensions similar).
The proposed hybrid electric production is probably because the PLAN isn't fully sold/confident on going fully electric, and/or the technology just isn't mature enough (maybe what the 057 class is most waiting on).
So, to sum up, I think, based on those rumours, that the 054B class will mainly be used to develop technologies for follow on programs.
One will likely be an 054A MLU programme, to retrofit the newer electronics, uVLS and sensors that will be tested and refined on the 054B class onto the existing 054A class. So in effect, the 054A class will probably be brought up to the same standard as the 054B eventually in all aspects bar propulsion.