In the first part of the talk I will discuss the connection between the bright QSOs and protocluster regions in the high-redshift Universe. Specifically, I will present new results which indicate that the baryonic processes in the assembling proto-clusters might be more complex than previously envisioned. This could explain why observed galaxies around bright QSOs are not providing strong support to the theoretical notion that the most massive black holes grow in high-sigma peaks. In the econd part of the talk I will review numerical uncertainties plaguing urrent state-of-the-art cosmological simulations of galaxy formation. I will then present global properties of galaxies as obtained with novel cosmological simulations with the moving mesh code Arepo and highlight which feedback mechanisms are needed to reproduce realistic stellar masses and galaxy morhologies in the present day Universe.