Most applications can use LDAP without any bind DN (anonymous bind). Only if you need access to posix account attributes (uidNumber, gidNumber, memberUid etc...) you can use a bind DN. In that case, do *not* use the admin or root DN: just create a standard SME user, and use its DN to bind (eg you create a user named ldapauth, the corresponding DN is uid=ldapauth,ou=users,dc=domain,dc=tld)
Using the admin or root DN and password brings no benefit, and just expose a very sensible password somewhere in clear text.
One more point: if you plan to use LDAP as an authentication source from another box, you *must* use TLS (port 389) or SSL (port 636), or SME will just reject the password, even if it's correct.
Regards, Daniel