The most important factor is the Coefficient of Lift (Cl) for the wing. As Cl increases (at lower speeds), the differential between lower wing and upper wing pressures increase, these being the origin of the wing-tip vortices. AoA, Load factor etc, all have a part to play, but put these 2 together to find the Cl that the pilot is calling for.
Wing tip vortices are reduced with flap set, unless the wing has full span equally deflected flaps. The outer sections of each flap assembly produce their own vortices, thus, there may be several sets of vortices, the total of which would be the same as for the clean wing, but are instead distributed between the various vortex generating lift surfaces, making each individual vortex of less energy than the wing-tip vortices standing alone.