BuddyPress.org

Unless you want to run multiple sites (the correct terminology, not “blogs”), you don’t need to run multisite. Regular WordPress will be fine.

There’s no technical difference as to how to structure your site. If you just want your site to look the same on the homepage, but for visitors to dive deeper before they get into “BuddyPress land”, then maybe sticking everything under what appears to be a directory would be best (take a look at the URL for this page, for example. We’re under /community but the main blog isn’t).