Marcus, G. Ding, Y. Emma, P. Huang, Z. Qiang, J. Raubenheimer, T.O. Venturini, M. Wang, L. TUP007 undulator electron FEL simulation emittance 2015 2015-12 High fidelity numerical particle simulations that leverage a number of accelerator and FEL codes have been used to analyze the LCLS-II FEL performance. Together, the physics models that are included in these codes have been crucial in identifying, understanding, and mitigating a number of potential hazards that can adversely affect the FEL performance, some of which are discussed in papers submitted to this conference[*, **]. Here, we present a broad overview of the LCLS-II FEL performance, based on these start-to-end simulations, for both the soft X-ray and hard X-ray undulators including both SASE and self-seeded operational modes.