Hello again,
One of the things that has not been directly mentioned yet is what power factor correction actually does, what it affects.
First, we can view a PFC circuit as being between the power line and the product. That means it acts as an intermediary between the line and the product such as a power supply. If we look at what it does for the product, it does not do much. That's because it's not really made for improving the product, it's made for improving something about the line itself. If we look at how it affects the line, we see that it has an important function and it affects the line by a significant amount.
This is why one method of correcting the power factor is done by placing a capacitor across the input line. If we think about this, the capacitor does nothing for the sine voltage, so the product does not see anything different. The line however has to constantly supply current to that capacitor and so the line gets affected by the change in current demand.
In the simplest case, the capacitor just has to change the phase angle of the current from the line. That means the impedance the line sees changes, but the product does not see any change.