Smart textile wearables (STWs) represent a transformative evolution in wearable technology, seamlessly integrating sensing, computing, communication, and actuation capabilities within textile structures. Unlike conventional wearable devices that rely on rigid electronics attached to fabrics, STWs embed functionality directly into fibers and yarns, enabling unobtrusive, comfortable, and washable systems for continuous monitoring and human-environment interaction. Enabled by flexible circuit printing, heterogeneous material integration, and miniaturized packaging, the system now achieves efficient fabrication of multi-scenario functional modules with stable low-power, wide-temperature operation. Notwithstanding these advancements, critical bottlenecks persist: material long-term stability, cross-module collaborative power consumption, and cross-device interoperability. Concurrently, the absence of unified ethical guidelines and performance standards hampers large-scale commercialization. This paper reviews component architecture, manufacturing processes, and evaluation frameworks, analyzing perception-response-processing-power supply collaborative design principles, comparing traditional and emerging technologies, and proposing a full lifecycle assessment framework from material innovation to industry compliance. Concluding with a synthesis of research progress, the paper explores future trajectories while highlighting pressing challenges in production and application domains for intelligent flexible wearable systems.