  Reduced quasilinear (QL) and nonlinear (gradient-driven) models with scale
separations, commonly used to interpret experiments and to forecast turbulent
transport levels in magnetised plasmas are tested against nonlinear models
without scale separations (flux-driven). Two distinct regimes of turbulence --
either far above threshold or near marginal stability -- are investigated with
Boltzmann electrons. The success of reduced models especially hinges on the
reproduction of nonlinear fluxes. Good agreement between models is found above
threshold whilst reduced models would significantly underpredict fluxes near
marginality, overlooking mesoscale flow organisation and turbulence
self-advection. Constructive prescriptions whereby to improve reduced models is
discussed.
