Two details about phase noise have been confusing me for a long time. Hope to be resolved
The Lorentzian describes that flat-topped behavior. [I initially wrote Lambertian, in error]

Regarding the DC power, cyclo-stationary statistics work in the 1990s validated the classic Leeson Equation. 

Today the simulators extend that statistical work into trusted predictors, to be within 1dB; fundamentally, the active device parameters including any distortion (and the spreads of those parameters) must be accurately known. This knowledge must include substrate-path modeling of charge flows; I suspect the non-linear effects of device isolation junctions become part of the cyclo-stationary modeling to describe transient behaviors and the resultant spectral folding.

Note the deterministic energy environment surrounding the active device may be quite large, and even balanced layouts may not overcome energy injection into inductors. varactors, differential-pairs, etc.

Most of this work has been written up in "The Red Rag" of the US's IEEE, the Journal of Solid State Circuits.

Here is a fine paper from Hewlett Packard (Keysight) on Lorentzian:
https://www.keysight.com/upload/cmc_upload/All/phase_noise_and_jitter.pdf

This is the first link encountered for "phase noise leeson equation".
http://rfic.eecs.berkeley.edu/~niknejad/ee242/pdf/eecs242_lect22_phasenoise.pdf