Low impedance of current mode circuits

Hi i am learning about current mode circuits. CMC (current mode circuits) have low impedance since the input signal current is given to the CMOS drain and not gate. Since by nature gate has high input impedance where the input voltage signals go. So when meaning CMC has low impedance does it only mean wer in the transistor do we give the input signal??? But in that case of voltage mode circuits VDS is given to a MOS transistor and current does flow from drain to source (NMOS) and this path doesn't have high impedance right??? Pls correct me if wrong.

2) Secondly i found online "The low impedance transforms them into low time constant circuits and the bandwidth is quite high."

The time constant is given by T=RC. So a low impedance circuit has reduced resistance effect and thus the time constant is reduced. (I am assuming this is the reason pls correct if wrong). But say in a MOS transistor we have the usual VGS and channel formed. How does a current mode circuit reduce the time constant of a circuit??? Also what makes the bandwidth high in current mode circuit than a voltage mode ckt??? Little confused. Can someone pls help!!!