Autocad is a good program for those things. I worked for a company years ago that used it, was still the MS-DOS version back then, before Windows was useable. They had a bunch of customized libraries and commands for their own use. Wiring schematics like this were very easy to do using the custom stuff they had. Unfortunately Autocad, even Lite or Sketch is too pricey for home use now that I am retired. Very nice drawings though!
AutoCad does give some flexibility, but like you said costs a lot of money. I have AutoCad, because I'm a Structural Engineer and need it for business. Lately I have been playing with Eagle CAD, which is free for electronic PCB design. Maybe that would be a good solution for schematics for layouts, but I can't foresee using it for control panels. I would maybe suggest using SCRAM or even a free graphics program for this as an alternative.