Modular Cable Organizer 3D Models

I already have an initial 3D file for a cable-routing channel and now want to turn it into a fully modular system that I can print on a consumer-grade 3D printer.

Here is what I need:

• Convert the existing channel into a repeatable module that locks into the next piece. I’m open to how that alignment works—snap-fit, magnetic, or even a small screw interface—so feel free to suggest the most reliable and simple (for the user) option for PLA.
• Design a square junction and a matching cap that let the run branch off at ninety degrees. The exact dimensions are still flexible; I simply need them to mate cleanly with the main channel and maintain a tidy exterior profile.
• Deliver print-ready STL files plus the editable source file (Fusion 360, SolidWorks, or similar).
• Ensure wall thicknesses and tolerances suit typical hobby printers (0.4 mm nozzle, 0.2 mm layer). A quick test assembly in your slicer to confirm fit is appreciated.

I don't have a lot of experience in 3D modeling for printing so if you have suggestion on how to accomplish the task differently I am open to it.

NOTE: By budget for this initial job (more will be following) is in the 60 to 120 dollar range, do not bid if you are not okay with it.