Small and medium enterprises (SMEs) in Vietnam face both opportunities and constraints in pursuing competitiveness through digital transformation and sustainability. This study developed a conceptual framework integrating four firm level capabilities - digital agility, innovation capability, sustainability orientation, and entrepreneurial resilience - with ecosystem and policy enablers. Drawing on case evidence from TECHPRO, EMES, and Menas, the analysis showed how digital tools, circular practices, and resilient cultures can accelerate growth, but also how structural barriers such as finance, regulation, and skill shortages hindered scaling. Comparative insights from ASEAN highlighted that coherent policy frameworks, including subsidies, incubators, and mentoring programs, amplified firm level initiatives. The findings contributed conceptually by linking dynamic capabilities with institutional support, and practically by offering managerial and policy implications for SME development. The study concluded that without reforms in finance, regulation, and skills, Vietnamese SMEs would struggle to translate emerging capabilities into durable competitive advantage.