On the topic of showing page progress with table of contents, author's description matches exactly how it is implemented in Material for MkDocs [1]. I moved my blog from WordPress to it (for unrelated reasons) and I immediately liked how going through longer blog posts felt with highlighted entry in the table of contents moving together with the page.
Just to be contrary, I find things on the page updating as I scroll to be distracting. I consider that kind of thing to be like a modern <blink> tag. On sites I read frequently, I nuke those elements with uBlock Origin. I guess I'm sort of a HTML fundamentalist, though.
[1] https://squidfunk.github.io/mkdocs-material/setup/setting-up...