I definitely agree, hkkmr. I was describing the general overview, but there's definitely a spectrum in both condition a) and condition b). You can range from knowing almost nothing about socionics, to knowing a bit about a few types, to knowing a lot about many types, to (in the best case scenario) having encyclopedic knowledge of all types. The same is true of understanding people: you can range from having a minimal and superficial understanding of an acquaintance or celebrity, to understanding basically how they think and feel, to having deep intimate insight into the inner workings of their soul.

In terms of how the type of the socionist affects things, I'd say that Intuition and Ethics helps to understand people's inner workings, while Intuition and Logic helps to understand the details of the theory. I know that STs, for example, seem to have fairly superficial estimations of people's personalities, while SFs often lack a sophisticated grasp of the theoretical details.