Comparison at z = 0 of the matter power spectrum (upper panels) and bispectrum (lower panels, squeezed limit (k₁ = k₂ = k; k₃ = 3k_f)) with respect a high-resolution reference simulation (see Section 3.3). The left panel shows the results for f_NL = 0 simulations, and the right panel for those with f_NL = 100. The line colour encodes the LPT order used for the initial conditions (red: 1LPT, green: 2LPT, and blue: 3LPT), while the line styles indicate the initial redshift. The shaded regions indicate the ±1% around the reference simulation. The results are nearly identical for f_NL = 0 and f_NL = 100. A later start using higher-order LPT schemes improves the agreement with the higher-resolution reference simulations.