Small and medium-sized enterprises (SMEs) increasingly depend on digital and financial resources, yet it remains unclear whether the benefits of these resources differ between small and medium-sized firms. This study examines whether firm size differentiates the relationships of accounting information system quality, FinTech innovation, digital financial capability, and financial literacy with SME performance. Survey data were collected from 165 SMEs in Bekasi, Indonesia, comprising 79 small and 86 medium-sized enterprises, and analysed using partial least squares structural equation modelling. Measurement equivalence across the two groups was first verified, after which the groups were compared using permutation-based multi-group analysis. The results confirm that all main constructs were measured equivalently in both groups. However, none of the six relationships tested differed significantly between small and medium-sized enterprises. In the full sample, FinTech innovation showed the strongest positive association with SME performance, followed by financial literacy, whereas accounting information system quality and digital financial capability had no significant direct association. The interaction between digital financial capability and financial literacy was negative and significant, while the interaction between FinTech innovation and financial literacy was not significant. These findings indicate that no company-size-based differences were detected in the relationship under study, without implying that the two groups are equivalent. The study underscores the importance of confirming measurement equivalence before comparing groups and suggests that SME support programmes should consider firms' actual digital and financial readiness rather than relying on size categories alone.