Mass ratio q distributions of BH–BH mergers (at redshifts z < 2.0) formed via an SMT formation scenario (colorful, continuous line) and a CE scenario (black, dashed line) for three tested models. The total sum of the BH-BH merger rate densities normalizes the provided numbers. Results shown are for our default model (upper panel), a model with high angular momentum loss γ = γ_L2 (middle panel), and a model with non-fallback decreased (full) natal kicks (bottom panel; see Sect. 2).