Hi Craig,
Thanks for checking out our plugins!
Yes, with Event Tickets Plus, you can require users to be logged in to be able to buy tickets. A ticket purchase with our plugin will not automatically create a new user.
As far as preventing new users from registering, that would be handled in WordPress itself (not from within any of our plugins), but you could accomplish this by going to Settings > General > Membership and unchecking “Anyone can register”. This way, if someone went to buy tickets, they would be taken to the login screen if they were not already logged in, but the “Register” option would not be available.
Please let me know if you have any more questions!
Thanks,
Jennifer