Question about using Sigil to convert HTML
I have 200 HTML files (extracted from secure eReader) that I want to convert---once and for all. I have experimented with manually cleaning up the HTML. I have experimented with converting it to RTF. I wind up with issues every time, and I am tired of re-doing them every time I switch devices. I want to make one more push through them, do it all now and wind up with a master file I can convert to mobi or to anything else, indefinitely and forever, without having further glitches and needing to do more work.
If I have a file which looks good in Sigil and I save it as epub, is it a clean file? Can I replace my buggy HTML master with it and use it forever like a commercial epub book (all of my commercial epub books have converted just fine to mobi). Is the epub code it generates cleaner than plain old HTML and I can be assured that things like em-dashes or curly quotes I might have forgotten to manually edit out will appear and be fine forever after?
I am just really frustrated with this seemingly never-ending editing I keep having to do, and it's a lot of files. I want a solution where I can slog through this one more time and have files I can keep forever and re-use on any device I have, error-free. I posted earlier about RTF being perhaps better than HTML but I did some experimenting since then and am still having issues.