When not generating vortex lift, was the airflow attached over both the upper and lower wing surface?
As the IAS decreased and AoA increased, the vortex started at the leading edge, and gradually grew in both size and contribution to overall lift until the vortex (or vortices) accounted for all the lifting force.
The simple answer is yes, it was attached flow.
The vortices never provided all the lifting force. Up to about 6 or 7 deg AoA there was no vortex lift, just the usual wing tip vortices. Above that AoA the non-linear (vortex) lift grew steadily until at stall (about 23 deg AoA) the vortex lift was around 45% of the total.