Re: pip install succeeds, ImportError on import
I'm not really familiar with installing Fiona on Windows. I could imagine that potential issues could be the wrong settings of environment variables, missing Visual C++ installations, wrong location of files or the Python 3.8 dll loading issue.
I would recommend you to try to stay as close as to our appveyor setup as possible: https://github.com/Toblerity/Fiona/blob/master/appveyor.yml
as this is proven to work.
As long as you don't intend to modify Fiona itself, there is no need to take the "hard" route. The easy route would be to use binary packages provided by either conda or https://www.lfd.uci.edu/~gohlke/pythonlibs/