Performance metrics (FoB in the top row and FoM in the bottom row) extracted from the Model 3 HOD samples as a function of the maximum wave mode k_max of the fit, assuming the rescaled covariance matrices matching the four Euclid spectroscopic redshift bins described in Sect. 2.3. Different curves correspond to different models, as described in the legend. The FoM panels are normalised in units of the reference FoM, corresponding to the one of the EFT model with all parameters free at k_max = 0.1 h Mpc⁻¹. The grey bands in the FoB panels represent the 68% and 95% percentiles of the corresponding FoB distribution, as explained in Sect. 4.1.1.