If you go to the Accounts section (sorry, don't use Outlook for Mac, so can't specifically direct you) where you've set up access to your e-mail server, it should tell you the type (hopefully) that you are using. You might be able to figure it out possibly by the server name, but a lot of them use "mail.severname.com" regardless of IMAP or POP, so that's not a definitive thing.
The thing about IMAP is that changes locally are reflected on the server, so if you end up deleting emails/folders and so on locally the result is immediately made on the server as well. And if that change was unintended, you end up losing it on the server with no easy way of getting it back.