Python

So you’re using Markdown cells for notes and not using code cells at all? This is a strange choice. It seems like just writing Markdown in a text editor, Markdown editor, or even an IDE with Markdown rendering would be better options. If you want to output the Markdown to other formats, pandoc is all you need. I’m not sure what advantage Jupyter gives you in this use case.

I find it pretty inefficient to start up a Python environment, a web server and a web browser to do something that you could do with Notepad or even in a terminal. I would use Notepad++, gedit, Kate, vim, vscodium... There are plugins for vscodium (and vscode obviously) to preview Markdown if that's what you need

To answer the first question, do whatever works for you, but I’d look at alternatives like Notable. It offers cross platform apps with sync using any desktop file sync service like OneDrive or iCloud.

I personally don’t see a point to using a Jupyter notebook for taking notes. You can create markdown files in Jupyter labs if I’m not mistaken, which is what I’d probably do, but I wouldn’t because I use Notable for that.

If this process works for you then sure! How you take notes is less important than building your body of knowledge with your notes.

Is it overkill? I think it is. Does it work for you? Go ahead then.

I installed a dokuwiki for personal use and it's great. Some people might say it's too much, but I'm happy with my choice.