I've never really had success doing concept work of any kind with pen and paper. Especially writing, but even diagramming. If I need to step back and work with ideas abstractly, the paper medium is still going to get in the way at least as much as the digital text does. What I really have to do is keep it all conceptual in my mind; that's the only medium that's truly unopinionated and flexible. Paper/whiteboarding is…
Also, I'm old enough to not have always had electronic devices, so sketching was all we had. In college, I didn't live on campus while living with my parental units an hour away. With the limited access to the computer lab, I would hand write code on paper and then transcribe. Then, right at the end of lab time, hit print so I could continue debugging by making notes on the greenbar print outs.