The Teams Pro guest feature is the best way to interview candidates, giving them access to a repl from which to demonstrate their skills. The amount of guests you have will not impact your seats, because guests are limited to only the repls they are invited to. Guests cannot access anything else in the broader team.
Here's how to invite a guest:
Navigate to the repl which you want your guest to work off.
Once there, click on the "Invite" button in the top right.
Through the modal, you have the option to invite someone with a guest role by sharing a link with them, or directly inviting them via their email address or Replit username.