If the CAD package can leverage GPU computing, then an eGPU is a good compromise. That way you can have plenty of power and airflow at the desk for intensive tasks, but you don’t need to lug all the hardware to the floor for interfacing with plc’s or to meetings. Although systems with good eGPU support are often expensive enough that keeping a separate desktop workstation and a lightweight laptop is competitive.
High single core cpu clock speeds and lots of ram should be the first priority for cad. Solidworks, for example, does not handle running out of ram gracefully at all.