Where is the field of each charge the strongest ?
(a. positive charge arrows pointed out)
(b. negative charge arrows pointed inward)

First we have to agree on what you mean by "strongest".

To me, "strongest" means the place where it exerts the greatest
force on another charge that happens to be passing by.

In both cases ... 'A' and 'B' ... that's going to be right smack on top
of the charge itself, or as close to it as you can get.

On drawings, it's the spot where the field 'lines' are closest together.

It makes no difference whether the original charges are positive or negative.