I run main power feeds to common points as required. Sometimes you'll need any combination of these but mostly a switched +12V is all you require.
Constant 12V
Accessory 12V
Start/Run 12V
Run Only 12V


I don't worry about using different grounding points unless you are working with precision voltage references like widebandss etc. I ground to the nearest metal framework and sometimes share multiple grounds just like tha factory harness. I solder whenever possible and heat shrink. I label wires extensively, use grommets at sharp points, use Velcro ties where re-entry is likely (they don't rattle either).
See photos for examples:

Main constant 12VDC feed to trunk area for accessories. Secured and grommets used at pass-throughs. Line is fused off battery with 40A fusible link.


Five fuses added inside main fusebox under hood. Keeps it neat and protected. Power tapped before fusible links.



Fuel sending unit mod. Heat shrunk and labeled.



Fuel pump re-wire. 30A fuse hidden behind armrest support, heavy wiring, wires labeled and secured, relay secured and grounded.


Accessory fuseblock added underdash for current and future gauges requirements.