You can derive hydrodynamical (and magnetohydrodynamical) equations in a rigorous (as opposed to empirical) way. BUT that gets you an infinite hierarchy of equations where the equation for the density contains the flows, the equations for the flows contains the pressure, the equations for the pressure contains the heat flux and so on. So in praxis we end this hierarchy at some point and "close" the system of equations by imposing e.g. a empirical description of the pressure based on density, flow and temperature (this would be an equation of state. you could also set the heatflux based on lower order equations and close there).
That said, yes there is deviation from what even MHD turbulence predicts for a stellerator. Gyrokinetic simulations are more complicated (you keep lot and lot of the individual particles that make up the fluid, but ignore at what angle along their gyro orbit they are, basically describing them as charged little rings), consequently much more computationally costly, but closer to real life. A full particle simulation (retaining pointlike particles with a correct gyro phase) with something like a PiC code would be even better but is indeed order of magnitude out of reach at the moment.
tl;dr: you have acquired a good high-level view via diffusion from the people around you.
That said, yes there is deviation from what even MHD turbulence predicts for a stellerator. Gyrokinetic simulations are more complicated (you keep lot and lot of the individual particles that make up the fluid, but ignore at what angle along their gyro orbit they are, basically describing them as charged little rings), consequently much more computationally costly, but closer to real life. A full particle simulation (retaining pointlike particles with a correct gyro phase) with something like a PiC code would be even better but is indeed order of magnitude out of reach at the moment.
tl;dr: you have acquired a good high-level view via diffusion from the people around you.