Like Routercnc I've found the best way of working if you need to see complete 3D assembly or work with 3D model is to create the components (or panels in your case) as individual 3D models on a single X/Y plane saving as seperate file. Then use these to make up an essembly of finished design to check every thing fits and looks ok, again saving as seperate file if needed.
Unlike routercnc thou I don't save extracted lines out as DXF's. When I want to cut 2D I just extract the edge's onto another layer and use these for the tool paths. If I want to engrave or cut 2.5D or 3D then just use the edges and surfaces of the model. All this is done from the same model which loads into my cam software.

Doing it like this you then creat a library of components that can be mixed matched and re-used at any time or used as template to be modified for one off custom's. It works good for ME.!

The modles are drawn and assembled mostly in Rhino and then loading into Bobcad Cam to create toolpaths. Bobcad can create 3D models but it's hard work compared to Rhino, to be honest it's not the best at anything (2D's not bad thou) but it creates the G-code I need ok and without fuss. . . . I wouldn't recommend someone buy it thou, the companys SHIT.!!

If I need straight 2D then 99% of the time draw straight inside Bobcad as it's quite good at this and I can go straight to cam. I can draw and have G-code produced for simple stuff like gantry sides, motor mounts even doors,draws or panels etc in minutes.