The only difference is the resistors that set the maximum output current. There are 4 switch settings on the board that set the current limit at 25, 50, 75 and 100% of the maximum. The original boards I looked at were set up for either 1.5 or 2.2A maximum. I have seen the ads for the 2.5 and 3.5A versions (the settings therefore are .6/1.3/1.9/2.5 or .9/1.8/2.6/3.5) but the chip is not going to handle more than 2.5A anyway without a bigger heatsink than the one fitted. At 0.5A and 24V these boards will be fine.

I'm sorry but I have no idea for KCam, never used it, but the standard setup for parallel port is pin 1 enable or charge pump, pins 2,3 X step/dir, pins 4,5 Y step/dir, pins 6,7 Z step/dir