Just to confirm I understand usage of this correctly:
If I mix individual users and groups as recipients of the same single message that gets the for this feature – will those individuals and all members of the groups get a copy of the message?
Also, for individuals who are a member of more than one specified group, or of a single group and also listed as an individual recipient – will they get a duplicate copy of the message?
Yes, groups are expanded to individuals when it is sent. If the same individual is included more than once (either as part of multiple groups or being manually added as a user) they are only sent one message.
for this feature – will those individuals and all members of the groups get a copy of the message?