I'm not sure I could even list all the authoring tools I've used, which includes writing a few college papers in nroff. I'd mostly stuck with straight text and graduated to HTML (the lingua franca of the Web) in the late 1990s. I actually got stymied on Lyx with some of its insistence on specific structures for documents and fighting those.
In the past year or two I actually took out my copy of the Lion Book and sorted out what I'd been missing with LaTeX. I realized that a decent set of templates was much of the issue, and now have a basic book and article template that I use for most of my work. And while futzing with specifics of layout can keep you from a final output, it won't stop you from writing. And that's the key problem most of the time.
I've also been exploring Markdown (thanks to reddit, Ello, Diaspora, and numerous other sites which rely on it), and Pandoc, which is nowhere short of amazing and astounding.
More often than I care to admit I'll take content from a website and either reduce it to its HTML core or, with depressing frequency, straight ASCII text, add back some light Markdown, and present it as PDF for reading. Web design has gotten that freaking annoying.
On the Medium discussion -- I find the site pretty good, actually, and disagree with the arguments Butterick raises against its minimalism. Good design is light design, and Medium is among the most minimally re-styled sites I visit. Changes?
.highlightMenu { display: none; }
.metabar--affixed { position: static; }
.metabar--bottom { position: static; }
.notesMarker { display: none; }
.postContent { color: black; font-weight: normal; }
Virtually none, by my standards.
Mind that I don't publish on Medium (at least, not yet). Though I've considered it.
As for "typewriter habits", among the advantages of the typewriter -- as a composing interface -- is that it simplifies input. Tools such as LaTeX then perform the job of transforming typewriter input into typographic output. Most often with very minimal additional directives from the author. Tools such as Markdown reduce that still further.
Two spaces after a full stop? Absolutely. Why? Because in my typography it helps me to distinguish between stops following abbreviations and sentences. Which is a useful thing. Mr. Brown. The first stop terminates an abbreviation. The second an entire sentence. About the only of the conventions that I need to consciously apply is ``quotes'' around quoted passages, though search-and-replace of "straight quotes" is actually pretty easily accomplished with some regex magick. Markdown removes the need entirely.