BuddyPress.org

if you want to allow your members to create blogs and go multisite, then yeah the members will have access to the backends of respective blogs. For site where BP is installed, members cannot access Add New Post unless you elevate their roles from anything other than Suscriber level which is default set in Super Admin Options.

For front end posting compatible with BP, https://wordpress.org/extend/plugins/one-quick-post/