Plots of some of the correlations tested for this work. Upper left panel: Γ vs. log(λ_Edd). We report for comparison the linear relations from Trakhtenbrot et al. 2017 (black dashed line), Liu et al. 2021 (black dot-dashed line) and Tortosa et al. 2023 (black dotted line); Upper right panel: v_C․IV vs. L_x, we also report the linear relation (black dashed line) and the combined 1σ error on the slope and normalization (grey shaded region) from Zappacosta et al. (2020). The empty dot is SDSS J0100+2802, which is not included in the fitting process given its different value of L_bol (see Section 5.2). The blue dotted line is the linear relation when including SDSS J0100+2802. We also report the linear relation from Zappacosta et al. 2020 (black dotted line). The v_C․IV values plotted here are, for simplicity, the mean values derived using all the available values reported in Table 3. We note that the fit takes into account all the existing values of v_C․IV (see Section 3.2); Lower left panel: Γ vs. log(M_s, Edd); Lower right panel: Γ vs. z.