Comparison of the 1D and 2D marginal posteriors for the noise-free benchmark spectrum from nested sampling (implemented by nautilus and MultiNest), FMPE, and NPE. For the latter two, we include the results with and without importance sampling. For visual purposes, we applied some light Gaussian smoothing to the histograms. Furthermore, we only show 6 selected parameters here; the full version featuring all 16 parameters is found in Fig. D.1.