Although differences between training and competitive contexts in table tennis are widely recognized, empirical evidence quantifying these differences remains limited. This study compared the technical-tactical characteristics of 40 training matches and 40 international competitions among Chinese National Youth Team U15 female players to provide evidence for training optimization. A mixed-method approach combining heat map visualization and Generalized Estimating Equations (GEE) was used to examine contextual differences and identify key factors associated with match-winning probability. Results showed that training and international matches exhibited similar individual technical-tactical indicators but differed substantially in placement-technique combinations and the influence of stroke sequences on winning probability. Training matches emphasized control of short areas, whereas international competitions showed greater use of backhand long-area attacks to initiate offensive play. In addition, early strokes were more influential in training matches, while later strokes played a greater role in international competitions. These findings indicate that current training matches may not fully replicate international competitive demands. Training should therefore enhance rally-transition tactics, offensive initiation, and competitive simulation to improve transferability to international competition.