Well I regularly try all clickable option in look and feel and heuristics. Mostly they are good enough. Then I inspect in the viewer (select text and right click) and use tweak epub.
But there are still enough that have me stymied. I prefer my books blank line between and no indent but some books not cooperative
I have used sigil, but it is a bit complex for just one book IMO. Maybe someday. Of course I am still lost in space at CSS and regexes for the most part but eventually I get it done. I am pretty good at search and replace though
Helen