No point in applying it to the back to top as this has a fixed position – so although it is hooked after the footer it should be displayed way before that is ever reached.
There have been reported issues with earlier versions of Chrome ( patched in Chrome 90 ) that content-visibility rules being applied to Landmark elements caused problems with the accesibility tree – so assistive technologies would not see them. So landmark elements such as <nav>
( which includes the #nav-below ) and <footer>
should be excluded.
For archives you would apply it to the individual post.
You can find a list of issues of the CSS3 Working draft git – see here:
https://github.com/w3c/csswg-drafts/search?q=content-visibility&type=issues
How many other issues that may arise, i don’t know… its why its best to tread carefully when applying any working draft or experimental CSS.