With plasma two different figures matter. Quality cutting thickness is the one at which the edge is fit for further work without grinding. Maximum thickness, sometimes called severance thickness, is a forced cut, with dross and a bevel. A 40 A machine cuts about 10 to 12 mm to quality, 60 A about 16 to 20 mm, 100 A about 25 to 30 mm, 120 A and more reaches 40 mm.
The second condition is air. You need a compressor giving a steady flow, usually 150 to 250 litres per minute at 5 to 6 bar for machines of 40 to 60 A, and more with stronger ones. The air has to be dry and free of oil, otherwise nozzles and electrodes are gone after a dozen or so minutes instead of a few hours. A filter with a dryer costs less than a set of consumables.
HF ignition is fast, but it interferes with electronics and does not like cutting mesh. Contactless pilot arc ignition copes with gratings and painted sheet. For CNC tables pilot arc ignition is the better choice, because it does not disturb the controls.
Check which consumables fit the torch. Torches of common types have cheap and readily available nozzles, rare torches can cost more than half the machine. In the listing we give the torch type and the state of the set of nozzles and electrodes that comes with it.