The key to cutting with accuracy and precision is not just within the plasma system. Plasma is an important part....at least 1/3 of the solution!
For excellent cut quality along with good accuracy.....and good consumable life....you must have a well designed torch height control that can sense the location of the plate surface acurately before each cut....which allows the pierce height to be set (1 bad pierce ruins the plasma nozzle...affecting cut quality)......and then indexes to cut height during the lead in portion of the cut....then quickly switches to arcvoltage control once the cut speed is achieved.
You also must have excellent x and y motion that can maintain the speed required by the plasma torch.....and should have acceleration in excess of 40 miligees.....this minimizes dross and ensures that the plasma gets up to its best cut speed quickly. There should be no jerkiness or roughness in the motion....any roughness in motion will show up in the cut.....any jerkiness (mechanical backlash) will create overshoots and divots in the cut.
Last, but not least.....the cut part program should pay careful attention to the shape and location of lead ins, lead outs, kerf width, as well as good resolution to make holes round instead of a series of connected straight lines.
Also....air plasma systems are the low end of plasma system capability! The Hypertherm FineCut consumable have a great reputation for cut quality on materials thinner than 3/16"......but for the best cut quality a high definition class HPR130xd plasma (also Hypertherm)....using oxygen as the plasma gas for steel...produces cut quality that will rival laser on materials thinner than 1/4", and is faster than laser on thicker materials.
Here's a few pieces cut with a Hypertherm Powermax45 air plasma with an entry level (low cost) PlasmaCam cutting machine...