Variance in the cleaned cubes as a function of the number of components removed: N_fg or N_L for PCA (dashed blue line), PCAw (solid orange), and mPCA (solid green setting N_S = 4 and solid red for N_S = 8). Horizontal stripes with corresponding colours highlight the variance level of the reference cube for each method (N_fg = 4 for PCA and PCAw and N_L, N_S = 4, 8 for mPCA), namely the solutions for each method that offer a maximised goodness-of-fit and amplitude when cross-correlated with the galaxy catalogue. For reference, the variance of the original, unclean cube corresponds to ≈9 × 10³ mK² and is characterised by the noise level highlighted by the dashed gray stripe.