The Pz. IV and below are classed as medium to light tanks, 12.7mm could have done significant damage to these but not really practical. The pilot will be more lucky, if anything to achieve a kill on tanks above Pz.II with .50cal.
One 20mm and one 37mm might achieve kills up to Pz.IV without lucky hits, but even then the Pz.IV could take a hit to its roof from a 20mm without damage. The 20mm and 37mm would have been better hitting from behind, and the 37mm could kill up to the Pz.IV without lucky deflections, and probably a few VERY lucky people could take out Pz.V Panthers with it. These were very heavily armoured tanks, and with such light armament, 12.7mm, 20mm and 37mm it would be very lucky to achieve good kills. Especially with only one cannon, slow rates of fire don't make up for its lack of hitting power.