Incomplete ideas, thoughts and jottings
Even less in writing than other disciplines, the tools don't really matter. Fancy notebooks are nice but not essential. Getting the words down is more important than the way you write them. Digital, analogue, it's all mostly the same.
What is important is the methods you use, rather than the tools you use. Avoid tool fetishism.
That said, if you do find a pen or a piece of software that helps you feel comfortable, use it more. If you can create less resistance it's good, but it shouldn't be your main focus.