Adaptive construction techniques in traditional vernacular dwellings play an important role in improving the wind–thermal microclimate of buildings. However, comparative studies on such techniques across different regions remain limited. Moving beyond a static regional perspective, this study selects six representative skywell dwellings along the historical migration route from Jiangxi to Hunan. Through field monitoring and CFD numerical simulation using PHOENICS, the wind–thermal performance of these dwellings under extreme summer high-temperature conditions is comparatively analyzed. The results reveal case-based regional differences characterized by “shared origins and regional differentiation.” The western Jiangxi dwellings tend to adopt ventilation as the main spatial logic, using open spaces to enhance convective heat dissipation. In contrast, the northern Hunan dwellings show more prominent shading and heat control characteristics, relying on optimized skywell geometry to achieve geometric shading and reduce radiative heat gain. This study clarifies that adaptive construction techniques vary significantly under regional influences, and the findings may provide quantitative data support and design references for optimizing the microenvironment of contemporary buildings.