If the current is not controlled, the lower the resistance in the water [ie higher conductivity], the higher the current goes. You get an upward spiral where the process accelerates out of control until the current maxes out and the voltage just stays at the maximum that the power supply will deliver. Some unregulated units will actually burn out if left unattended..and make a mess. I have seen these unregulated units for sale as low as $19.95. That's about what they're worth. I've also seen them sell for $150...and more.
They consist of 3 nine volt batteries in series to deliver 27 volts..all the time. Most, but not all, have a resistor or small light bulb that 'limits' current to a set maximum ,so, to be fair, most do have 'some' sort of limit so they won't just heat up, boil water and burn out. I highly doubt that they will produce a uniform particle size. By all indications, the particle size will start out being small and continue to grow. None of this type will produce a clear CS beyond around 5 or 10 PPM and most won't even do that.

You 'can' make decent CS with those generators, if you have time to watch it really close and hook up some manual controls and monitering instruments.