Fraction of pair-ups occurring within migration traps (left panels) and pair-up efficiency (right panels) as functions of SMBH mass M_• (top row), migrator mass m (middle row), and initial radius R_init (bottom row) in the K18 prescription. Color encodes the viscosity parameter α (orange: 0.01; teal: 0.1; navy blue: 0.4), and the two torque prescriptions are distinguished by marker shape and line style (squares and solid lines: G24; circles and dashed lines: B16).