To me, each format has its own uses, and they are pretty well separated.
Anything I do for myself, I do with pen and paper. Solving a problem (you know, formulas and equations), taking notes when reading a paper or book, recipes for Stardew Valey, Hearthstone Arena log, Doodles, To do lists, Purging internal rants....
If I think I don't have enough to fill a notebook per month, I come up with things to do. Not Kidding.
Anything that involves collaboration with others or needs to be read by others, I do digitally.
The only time there was considerable overlap was when I wrote my thesis. I would write down my notes/ thoughts/ideas in bullet form on notebooks. Plots, 3D rendering and diagrams I did on my PC of course. When I felt I had everything I needed for a chapter I would write it all up on word processor.