Within this LE consideration, the output current (capability) does
not vary, the output current (or impedance) -- for any gate which is to be compared to an inverter -- is kept constant and equal to the inverter's output current. As
checkmate explained above, for this goal you need respectively more and/or larger transistors. The input capacitance of all the transistors needed to achieve the standardized output current in relation to an inverter's input capacitance (3 std. cap. units) is the LE of the resp. gate
input.
This is standardized for Kn/Kp=2, i.e you need 2 PMOS units to deliver the same current as 1 NMOS unit, which also means 2 std. PMOS input cap units in comparison to 1 std. NMOS input cap. unit -- that's why an inverter needs 3 input cap. units. The LE is always related to 1 single input.
For different output drive capabilities the LE comparison values may be different, see this image below:
Also for complex gates, different inputs could own different LE values.
HTH! erikl