My course has an in class live component - and I would like to send a custom email to that group for the logistics of where and when. I teach seminars in two different cities. I know I can copy my course so each course reflects a location - but the only real difference between the two courses is where the seminar is held.
This is certainly possible to send a custom notification to students in a specific course - you can use the Filters option from the Users report in the Admin Dashboard. You can filter per a specific course and then craft an email to them.
In terms of having seperate courses, yes, you can duplicate and change the relevant details. That may be the best way to go to help keep students group seperate.
Hope that helps!