1. no sitemap needed/required to get the preferred url working
but choose the one u used yourself mostly to point to your site
and make sure you use it that way to link to your home from other pages and sites, and get others also to link to you with the proper url.
2. apache server is fine to do the .htaccess
don’t worry to much about this issue
e.g. capeuro.com and asop.com are also reachable with and without www and don’t seem to have a problem….lol