It depends on the change I need to make. Most rig elements are encapsulated into classes that I can “sync” to and have full introspection as if I just built it. It also depends on how the information I’m editing gets used, whether it gets saved out as an external Maya file that is imported during the build process or perhaps it gets saved out into a weights file if it’s a skin cluster or maybe its component positions for animation controls and etc. So yes sometimes I rebuild it, sometime I edit and save the data granules out, sometimes I spit out new code to replace the auto build.
The node tool has access to any nodes you as a user have defined for it. It doesn’t natively hook into anything, rather it’s a node based access to my rigging libraries that are exposed to it. The end result of it is an executable solve of the graph (something like your the auto rig or a publish script)
At the moment it supports Python and MEL for node definition and final executable.