Under-forest wild-simulated cultivation of Gastrodia elata Bl. f. glauca S. Chow (Wu Tianma, WTM) offers a viable pathway for reconciling ecological conservation with economic and health benefits, yet optimal seed tuber regimes remain understudied. We established nine planting regimes varying in single-tuber weight and per-hole dosage in a karst plateau area, monitored tuber yield and bioactive components (gastrodin, p-Hydroxybenzyl alcohol, and parishin), and evaluated performance via one-way ANOVA and a comprehensive index. At equal per-hole dosage, individual tubers of 10–15 g achieved the highest comprehensive index (57.13%), whereas those <5 g performed poorly (28.66%). With respect to seeding rate, the maximum yield (5.27 kg/m²) was achieved at 250 g per hole, while the highest combined content of gastrodin and p-Hydroxybenzyl alcohol (0.29%) and the peak parishin content were observed at 350 g and 150 g per hole, respectively. While tuber weight and seeding rate significantly affected yield, they had minor impacts on bioactive composition, suggesting that medium-sized seed tubers with moderately increased dosage can synergistically improve yield and quality. Our findings provide empirical benchmarks for germplasm selection and agronomic optimization in WTM cultivation, and call for multi-scale studies integrating soil microbiota and microclimate to unravel cascading mechanisms for sustainable quality enhancement.