Looks like the design team worked hard to minimise changes and maximise parts commonality with the single seat A as a design priority.
Another priority seem to have been to maximise rear seat visibility, which suggests that being a trainer is a core design requirement, as we always knew it would be.
Both of those factors together pretty much determined the hunchback look.
The spine changes looks to be a evolutionary improvement on the J10S' avionics spine to make it blend better to the fuselage.
But I think it is most likely a similar avionics spine over a mini-conformal fuel tank. Mostly because there is just nowhere else to put all the avionics displaced by the second seat. So unless they want to make the JF17B a pure advanced trainer, they have no choice but to use that space for mission avionics.
Given that, I would expect the JF17B to have shorter range than the single seaters, which would restrict their usefulness as strikers.
But, given the most likely adversaries and missions the PAF might fly, either they will be doing bombing missions against insurgents with no air threat, or they will be playing defence against the IAF, I really don't see deep strike as a core requirement for them.
An area where the JF17B might excel at OTOH might be EW.
I would not be surprised if we see the JF17B get dedicated EW and jamming pods like those sported by the JH7A and function in a similar way as mini-growlers to support a friendly fighter formation on AA or strike missions.
