I864, I864A, do we really need

them for dependents of employment-based I485? There once was a discussion here, but no clear conclusion. As I know, different people have tried different approaches:
Nothing
Notarized I864 only
Notarized I864A only
Latest paycheck, W2s, Tax returns (in dependents' petitions)

(Obviously some questions designed on I864/I864A do not apply to this case)

Your thoughts are highly appreciated.