Yes of course. You can use the add-on with any custom object you wish to place along a curve. For the best outcome build your assets facing the X-Axis.

Yes. Simply replace the geometry node tree in the chain's nodes modifier with your custom node tree or use a whole different set of modifiers. (I plan to add a cable preset in the future.)

The default color of empties is black. You can change it in Blender's preferences. Go to the "Themes" tab, expand the "3D Viewport" category and change the color of "Empty" to whatever suits your needs.

The relationship lines indicate the connections between parented objects. You can turn them off in the 3D Viewport overlays. Unfortunately Blender doesn't provide an option to hide relationship lines per object.

Chain Crafter currently supports only NURBS curves, therefore other spline types need to be converted to NURBS first and the process doesn't generate identical splines.