Hi,
You can use the KLMK2 to control any hardware that use classic MIDI protocol and/or Control Voltage.
If you wish to use it without a computer yes you need to buy a separate power supply.
In User Mode, all parameters (pads, encoders, sliders, wheels, CVs etc...) are editable directly from the hardware if you don't want to use a computer and the Midi Control Center.
Regards,
Matthieu