I've played with Sketchup quite a bit (just for designing - not building) but am looking for an alternative.
I've tried FreeCAD, and my head imploded. I loathe the hostage-ware philosophy of Fusion 360. TinkerCAD looks a bit primary-school-crayons, but I'm probably being unfair.
Am currently looking at Blender, but that's more movie-GFX than milling-machine-isometric, so I'm not sure that's the way to go yet.