The Powermax 30 was designed for hand cutting at relatively low duty cycles on thin materials. That being said, there are many of these plasma systems in use on cnc machines.
The cutting specifications for using the Powermax30 that are listed in the manual are for hand cutting. A good rule is to cut at approximately 60% of the speeds reccomended for hand cutting...when you are machine cutting. That should solve your cut quality issues. The cut height and pierce heights that (1.5mm for cut height, 3 mm for pierce height) should be good.
I would not recommend using the Powermax45 consumables in the Powermax30 torch...as the air flow rates and pressures will not be correct, and could cause issues with consumable life and possibly torch damage. I am not sure that they will fit in the Powermax 30 torch as well.
You can use .5mm cut height on stainless steel for good results, but use 1.5 mm on carbon steel.