It would be useful to print a wiring only preview of the house in 2D/3D

This can be achieved by using levels as layers. You add another level at the same elevation of the current one (let's call this new level "wirings layer").
Then, while keeping the wirings layer selected, draw the wirings using the plugin. If you have already placed wirings on the wrong level, select them, use the cut tool (ctrl+x), then select the wirings layer and use the paste tool (ctrl+v).
Now you are able to hide/show independently wirings and/or the rest of the home.

NOTE: to take a picture of the 3D view with wirings visible, you can't use the photo tool. You have to capture the screen using any tool provided by your operating system. This is a known limitation.

is there an option to add wiring conduits and perhaps these could surround the wires?

This was an old idea I had in mind, however I have not defined a plan to implement this feature. It certainly won't came in the next release, but it could in the following one.