In Dopus, if I open a password protected zip or rar file (say Misc.txt) and make edits to it, those edits are not then saved to the compressed archive as they would be with WinRAR. Is there something I'm overlooking or doing wrong?
If you double-click a file in an archive (password protected or not) and open it in an external editor, the file is extracted to temp and the editor is only editing the temporary copy. It isn't recompressed back into the archive automatically. (That's something we offer for files on FTP sites, but not files in archives.)
You would need to copy the file out of the archive, edit it, then copy it back in again. (Or use an editor that understands files in archives, and tell Opus to pass it the path within the archive instead of extracting it to temp. Opus can do that, and some editors support it, but it's not that common for zip and extremely rare for RAR.)