This is one of those times I entered a web search knowing what I was looking for already existed:

=>https://jedhernewriter.wordpress.com/2017/09/03/4-and-a-half-reasons-why-courier-is-the-best-font-for-writers/

I have taken to writing my longer (in my case medium-sized) pieces in simple text editors -- notepad when I am on my windows box, "texteditor" when I am on the work-computer Mac. In both cases, I like to switch my font over to Courier (really Courier New).

With perverse pleasure, I inform you that I take these masterpieces of general computing and I turn them into a large white sheets to write upon. I have played around with even more minimal editors, such as Pico, but I find that the ability to use a mouse in placing my cursor and to manipulate copying and pasting actions is useful enough to warrant using them.

Looking into my heart, the real thing I want is speed of response. I never want to see a lag between my finder hitting a key and the letter forming on my screen. And so -- hey, hey, ho, ho! Google Docs and Gmail has got to go! At least as a drafting tool when I am trying to do that elusive deep work.