Current paradigm suggests that the Ohmic electrical response of nanochannel-microchannel systems is determined solely by the nanochannel while the effects of the adjacent microchannels are negligible. However, recent works have challenged this paradigm and have shown that at low concentrations the microchannels contribute in a non-negligible manner. As such, the two favored models used to explain experiments are inadequate in describing realistic nanochannel-microchannel systems. To partially reconcile some of these issues, two newer nanochannel-microchannel models were derived and suggested as a suitable replacement for the nanochannel-dominant models. Unfortunately, these two models are limited to either very low or very high concentrations. In this work, we review these four leading models. We discuss their key assumptions, advantages, shortcomings, and present a knowledge gap between all models pertaining to the effects of the microchannel resistance for all concentrations. To overcome this gap, we derive an analytical solution that accounts for the effects of the microchannels and holds for all concentrations. This solution unifies three of the existing models where we show that they are limiting cases of our more general solution. We are also able to disqualify the fourth model. Our derived solution shows remarkable correspondence to simulations and experiments. The insights from this unifying model can be used to improve the design of any nanofluidic based systems.