Distributions of the inferred CO(2-1)-to-CO(1-0) ratio (R₂₁, left) and CO(1-0)-to-H₂ conversion factors (α_CO(1–0), right). These quantities are derived using IFU maps from models described in Equations (13) and (14) (for α_CO(1–0) and R₂₁, respectively). Histograms show median R₂₁ and α_CO(1–0) calculated across the full maps (global, empty black histograms) and tapered maps (beam, grey histograms). The red (blue) dashed lines indicate the median of the global (beam) quantities, while the green dash-dotted lines show the typical values adopted for star-forming galaxies in the local Universe (e.g. R₂₁ = 0.65 and α_CO(1–0) = 4.35 M_⊙ (pc² K km s⁻¹)⁻¹). Regarding R₂₁, we measured medians (depending on the coverage) generally lower than the average values observed in nearby galaxies. The α_CO(1–0) values span an order of magnitude, with lower conversion factors measured within the galaxy centres. This is consistent with the fact that galaxies exhibit a declining metallicity trend with respect to the galactocentric radius, hence showing lower α_CO(1–0) in their centre (see also Appendix A).