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Preferential flow in porous media is commonly encountered in many practical applications. Under preferential flow conditions, the multiphase displacement process is significantly affected by the wettability and disorder of the matrix structure. Our previous studies have discovered the preferential flow-induced nonmonotonic wettability effect by microfluidic chips with the preferential flow pathway and paralleled strongly disordered matrix structure, but the impact of the interplay between the disorder and contact angle under preferential flow conditions is still not well understood. Here, we combine microfluidic experiments and pore-scale simulations with theoretical analysis to study the impact of the disorder on the invading process from strongly water-wet to strongly oil-wet. Even though varying the strongly disordered matrix structure to a uniform state, the generality of the preferential flow-induced nonmonotonic wettability effect is still proved. However, the previous theory cannot explain the invading behavior in the uniform matrix structure. New mechanisms for the uniform matrix structure are further investigated by pore-scale modeling, which indicates that the balance of imbibition ability at the pore scale and the interfacial stability of macroscopic patterns dominate the invading process. We derive a theoretical model to describe the wettability effect and predict the optimal contact angle, which fits well with experimental and simulation results. Our work extends the previous understanding of the impact of preferential flow conditions on the wettability effect and is also of practical significance for engineering applications, such as geological CO2 sequestration, enhanced oil recovery, and soil wetting.