Yes, DC power can be used. A good range is 22-27VDC. Do not exceed 27VDC. When using DC power, you must connect it to the Just Plug Light Hub, not directly to your lights. Using less voltage will cause the lights to be dimmer, but still operable.
Yes, you can mix different styles of Street and Wall Mount Lights on one Linker Plug, just be sure not to exceed the number of lights in any one package.
The product was designed so that the number of lights in each package can be connected to the included Linker Plug.