Hi
Unfortunately, I don't have any experience with Cadence, have used nonlinear simulators in ADS, MWO and long time ago in Serenade from Ansoft. All the nonlinear simulators that I have used were harmonic balance simulators. Not sure, but guess that most time domain (Spice based) simulators should work without any problems (some might have problems if negative L and C values have been used in transistor models - the response becomes non-causal).
First of all, it is a must that you have non-linear model of transistor. Then it is just the matter of setting the simulations, varying the component values and viewing the results, as usual. If non-linear optimization is not available you can use manual adjustment of component values to maximize output power/efficiency. Generally, I think that any RF/Microwave part of your circuit should be analyzed using nonlinear tools. The working regimes of the devices are strongly nonlinear.
flyhigh