Does it replace spaces and underscores with dashes?

” ” and “%20” already converted to “-” by WordPress core.
“_” is left untouched by WordPress and by Filenames-to-latin plugin.

Thanks for the info.

Just in case you ever consider adding the underscores-to-dashes conversion, there are some good justifications at https://www.webmasterworld.com/google/4533254.htm (the one I currently prefer is enhanced visibility).