I am a beginning PhD student studying topological materials and strongly-correlated systems, such as high Tc superconductivity. I am using density functional theory in my work. I am wondering what I need to know in order to master DFT calculations using vasp (and also QE). I currently have some level of understanding of the theoretical basis of DFT (the Kohn-Sham equations, the Hohenberg-Kohn theorem, the Levy-Lieb functional etc.), but I do not have a lot of understanding on the pseudo-potential formalism (e.g. PAW), and the algorithms used in VASP to calculate the electronic ground state (e.g. the blocked Davidson algorithm and the RMM-DIIS algorithms).
I am wondering if it pays to spend time trying to understand how the DFT code actually works and if so, what is the best way to do that. My principal goal is to do DFT calculations to understand topological systems and strongly-correlated material systems. This involves building tight-binding models etc.