New Plasma build question

Minimum water level under the cut level of the torch is around 40mm, having space under slats is nice so the water can level and escape during cutting, having a bit of water above the metal plate being cut is really nice as it gets rid of the little bit of dust, running it submerged is the best way but not preferable for systems with part time use as it will corrode the torch. Adding baking soda to the water will keep the table in a nice condition for many years as it does not allow corosion while the slats are under water and it also reduces the smell of water wapor.
Scratch start will be a challenge, but I think firing the torch before probing could just make it work, but only with floating head and switch. This will also have the inheritable problem of short circuiting the output of the plasma cutter while probing and while that is required to make it start, doing that very often and for prolonged time might end up in burning the plasma if it does not have provisions for limiting the output current, that can be checked easily by opening the plasma and looking for a choke. Ohmic ( I do not like the term as it has nothing to do with the procedure not is being used for ) can not be used with scratch start as it will send all of the output voltage and power to the sensing equipment, rendering it "on fire ".
As for 10 or 300, in your case most probably the 300 since you do not have HF/HV start and most probably your plasma source does not have a built in divider.