This contribution presents a detailed microstructural and chemical investigation of Sm2(Co,Fe,Cu,Zr)17 sintered permanent magnets with different iron content. A major objective was to use atomically resolved STEM-HAADF Z-contrast imaging in combination with micromagnetic simulations to directly determine the atomic structure of the pinning relevant phases (1:5 and Z-phase) and their magnetic behavior. Low iron content leads to superstructure type ordering of the Zr-rich platelets, which contribute to the formation of a well-developed 1:5 phase and thus a diamond-shaped cellular structure. The coercivity is dominated by the density and strength of the pinning sites in the 1:5 phase while modified by the Z-phase. Via direct atomic scale observations we demonstrate that Zr preferably replaces the Sm atoms located at the Sm1 (6c) site in the SmCo3 structure yielding a modified structure with the following sum formula: Zr2SmCo9. This enables a comprehensive way of tailoring the magnetic properties, for example, coercivities since Zr favors Z-phase nucleation and controls diffusion along the Zr-rich platelets stabilizing the diamond-shaped cellular 1:5 phase. An enhanced understanding of the pinning mechanisms in Sm2Co17 yields a viable route to apply these thermal and chemical protocols for improved magnetic performances also to other systems than Sm2Co17. Further studies in this material system focusing on nanoscale spin dynamics and on the redistribution of elements like Cu and Zr on the nanoscale during different annealing programs as well as structural and chemical changes after doping by other rare-earth elements will be carried out in the near future and are beyond the scope of the present contribution.