Depends on your location.
Depends if it is an existing house, new, or renovation.
Being a rental may make a big difference.

Wouldn't be easier to ask the AHJ what they would like to see?

Not in the NEC.

Look into the mechanical codes.

"Wouldn't be easier to ask the AHJ what they would like to see?"

I'd much rather find out what the actual code is and go by that.
I don't care much what an inspector "would like" to see.

If you're the homeowner and the code says that the detectors need to be hardwired with interconnect and the AHJ says the battery type is just fine, are you going to start running wires?

This is the kind of question a quick phone call can resolve. If you don't like the AHJ's answer, then start looking for the code.

You don't say where you are, but it's most likely in one of the other codes. In NC, for example, for residences it's in the North Carolina Residential Code which is derived from the International Building Code