Depends on what you mean by this.
If you mean defining terminal name, it depends on if you want to be able to constrain rules or buttons to show or not show on specific terminals.
If all tills are going to have exact same layout and options then you would only need terminal x1 in theory but probably good ideal to make 5 terminals so you can define options between them.
Yes you would have one machine which will run the SQL database, the terminals will just have samba without a database and link (via network) to the server machine and the database it hosts.
Not quite sure what you expect for another idea? that is the way it works, ‘server’ machine with database and ‘client machines’ with samba installed and linked into the one database.