The influence of hydrothermal synthesis, thermal post-treatment at 500 °C and Mo content on a series of Bi1-x/3V1-xMoxO4 (0.02 < x < 0.15) photocatalysts was investigated for methylene blue (MB) degradation and O2 evolution. As Mo incorporation stabilizes the formation of tetragonal BiVO4 phases, only calcined Bi0.99V0.98Mo0.02O4 compounds showed good photocatalytic performance in MB decomposition. The Mo-induced blue shift of the band gap thus outweighs the positive influence of Mo-induced morphology stabilization and surface reactivity enhancement in Bi1-x/3V1-xMoxO4 materials. Both BiVO4@TiO2 and BiVO4:Mo@TiO2 heterojunction composites with TiO2 particle coatings in the 10 nm range were newly synthesized and displayed improved photocatalytic performance in MB degradation. Comparative studies with SnO2 heterojunctions revealed a superior influence of TiO2 deposition over SnO2 coating on both BiVO4 and Bi1-x/3V1-xMoxO4 oxide substrates. Different synthetic guidelines for BiVO4-based solid solutions and heterojunctions in photocatalytic wastewater treatment and water oxidation are discussed.