An experimental and numerical investigation was carried out to explore the effects of four vortex generators (VG) on the onset of flow instabilities, the paths and characteristics of the induced coherent counter-rotating vortices at a Reynolds number Re ≈ 2000. The flow field around the VG was characterized using a smoke visualization technique and simulated numerically using Reynolds-averaged Navier-Stokes (RANS). The taper angle of the VG was varied based on the used tab geometries, including triangular, trapezoidal, and rectangular tabs, which shared the same height, inclination angle, and base width. The results reveal that each VG was able to generate a counter-rotating vortex pair (CVP), and that the taper angle has direct effects on the path of the CVP, the onset location of Kelvin–Helmholtz (K-H) instabilities, and the circulation strength of the vortex structures. Furthermore, a linear relation between VG taper angle and the onset of instability was observed experimentally. Before the onset of K–H instability, the path of the CVP in the wake of a VG can be predicted using a pseudo-viscous model, which was validated numerically and experimentally.