B) realization that modules by default will increase the power level of the game
Yes and no, depending on what "modularity" are you talking about.
For example, "skills" and "feats" can be seen as character creation modules. If you use them, then all your PCs are going to have various bonuses to checks and some special abilities. They are therefore more powerful.
But a rules module, for example the often mentioned tactical module, is not going to increase the PCs' "numbers" directly, but eventually it's going to increase only their flexibility.
Now, I am the first to advocate that flexibility
is power, in fact, but only if you are able to use it properly

In the hands of lousy players, it can actually even make the game more difficult.
If the game has a CR system for encounters, then it might be possible for the designers of a module to suggest adjustments to your encounter. XP alone may or may not suffice.
But then I'm not even sure it's so much needed to provide adjustments if each module doesn't make that huge difference... perhaps the best is to rely on the DM's judgement. I mean, you can make a couple of mistakes (hopefully unbalanced in favour of the PCs) when running your first adventure using a new module, but then you see how it goes and adjust the following encounters accordingly.