High entropy alloys (HEAs) have triggered significant scientific interest due to their unusual structural stability combined with excellent mechanical and other functional properties. Recently, the high-entropy concept has also been applied to the field of protective coatings. We use ab initio calculations to provide an unbiased insight into their behavior at the atomic level. Namely, we focus on the interplay between high entropy (chemical complexity), sluggish diffusion, and (local) lattice distortions in the example of high configurational entropy sublattice nitride (HESN) ceramics. We show that the high entropy itself is not a guarantee for the sluggishness of diffusion (as quantified by migration barriers). Next, we propose a relation between the local distortions (measured by the width of lattice bond length distributions) and activation energies. The presented results provide examples that the core effects, characterizing the exceptional properties of HEAs, are system-specific and hence highlight the need for analyzing each system of interest individually.