Hi,
first let me say that if you don't need internal redirects of complex destinations probably you don't need the Enterprise version.
About your questions,
generally speacking, what you do with .htaccess can remain in the .htaccess.
1— www or no www go to the url
If you mean the redirect from the www to non-www or viceversa, the current ReDJ version is not able to do this because it works only with REQUEST_URI. The next ReDJ version for Joomla 1.6/1.7 that will be released maybe tomorrow will be able to do this...
2— Hidden subfolder in url (all my sites are in subfolders)
If I get what you mean, this MUST be handled by .htaccess file.
3— finish with a permanent redirect (301)
ReDJ can handle any 301 and 307 redirect.
If you have more questions, let me know.
Luigi