Fig. presents the population dynamics of the polariton states and the dark states for model 3, which varies the single-molecule coupling strength g c from 40.8 meV to 96.1 meV, while keeping the other parameters fixed. Again, all trajectory-based methods are able to qualitatively account for the relaxation of the upper polariton state into the other states. However, both MQC methods (MFE and GFSH) predict a slower relaxation rate and a larger steady-state population for the upper polariton state compared to the HEOM results. Looking at the transitions into and out of the dark states, we observe that both MQC methods are only able to qualitatively capture the increase in the total dark state populations. After the dark state populations have reached a maximum value, both MQC methods predict little changes in the dark state population, which is in contrast to numerically exact results from the HEOM method. Consequently, the lower polariton population calculated from both MQC methods is consistently underestimated compared to the HEOM method.