Mean variance of the δ distribution measured in five radial bins normalised by the virial radius, r_vir, for each model. The FCT model shows the largest variance, especially near r_vir, highlighting the effect of PBH-induced substructures. We also explore the separate contributions of haloes with M_h > 10⁹ M_⊙ (potentially luminous) and those with M_h < 10⁹ M_⊙ (dark subhaloes). The larger signal from the luminous component suggests that observational detection through radial luminosity fluctuation profiles may be a promising method to constrain PBH scenarios.