Background: Fission modes in superheavy nuclei are expected to be impacted by quantum shell effects. Similar shell effects may be present in quasifission reactions, acting to hinder the mass equilibration process in heavy-ion collisions.Purpose: To investigate quasifission mechanisms in five different reactions forming 294 Og as a compound nucleus and compare quasifission trajectories with predicted fission modes.Methods: The potential energy surface (PES) of 294 Og is calculated using the static Hartree-Fock approach with BCS pairing correlations. Quasifission trajectories for central collisions at various energies are studied with the time-dependent Hartree-Fock theory.Results: The exit channel strongly depends on initial mass asymmetry and orientation, but it only exhibits small dependences in the reaction energy. The 48 Ca+ 246 Cf reaction is affected by the PES topology, leading to either fusion or asymmetric fission. Spherical shell effects associated with the Z = 50 magic gap hinder charge and mass equilibrations in 126 Sn+ 168 Er, resulting in large total kinetic energies and compact scission configurations.Conclusions: Quasifission trajectories can be interpreted in terms of the underlying PES for low excitation energies. Future investigations of quasifission with temperature and angular momentum dependent PES could be considered.