It will probably be next week before I can check out QGIS solutions.
From the user's perspective, even if off in a few spots, several of these LISP solutions here are faster (maybe more accurate), even including time to adjust manually than most of the other solutions for GIS, though I am no speed demon in GIS.
Just look at all of the prep work on the Whitebox Tools, though if I had all of those branches and islands as well as a few oxbows, thin connections, etc. like the example, that would be the way to go as far as I can tell, I do believe it also works on vector, IIRC.
It looks like part of that is free as a Python toolset, I'll try to read up some more on that.
As I mentioned long ago in this thread, my daughter's co-workers are using AutoCAD to create the centerlines and manually adjusting if needed even though they have ArcGIS, though they may not have the extra tools that have the easy centerline tools. From what I looked up, ArcGIS made some tools a higher priced tier.
Maybe asking a few questions on some GIS forums might yield more information.