Outflowing velocity (v_out) plotted against ionization parameter (ξ) (panel a) and distribution of hydrogen column density (panel b) of a radio-loud (RL) AGN 3C 59. The black stars are the best-fit results obtained by the spectral fitting strategy that we adopted in this work. The symbols with gray edges represent the best-fit results based on different spectral fitting strategies: spectral fitting without NIR-optical-UV data and adopting different SED compositions (Test 1; green triangles) and spectral fitting with inclusion of the EPIC-pn spectrum in the energy range of 0.3−2 keV (Test 2; yellow circles) (see details in Section 4.4). The red squares are the best-fit results for a radio-quiet (RQ) AGN NGC 3227, which are derived from Wang et al. (2022b). The v_out − ξ relations of the radiation pressure-driven (dashed gray line) and MHD-driven (dotted gray line) mechanisms are scaled to the average values of WA_H and WA_L of 3C 59 (two black stars).