what does cmos 2 * lambda = l
Unfortunately, for the sub-micron technologies, there is no easy design formulas where you can use the quadratic equations. You can still use them to approximate the answers (very approximate), but in this case you also don't need accurate values for lambda and uCox. So, I guess, any value that you can extract from simulations will be OK, but will not be accurate.
ro of the transistors is changing with Vds for constant Vgs anyway, so lambda has little meaning nowadays. Plus if you try to extrapolate the Id(Vds) curves of a transistor, they don't intersect at one point on the x-axis (Early voltage).
For good design practice try to search matterials about gm/Id based design approach.