Hi Tracey,
Thanks for your post - this is a great question!
Both options are possible, and I would say it completely depends on the time of your visit. Holiday seasons and weekends can be a lot more busy, and in this case booking ahead is highly recommended. The entry to the exhibition is based on time slots and booking ahead ensures you don't have long waiting times. Certain tours, like the 'Discovery Tour' must be booked in advance.
The Titanic Belfast website is very informative and you can find a lot more information on their bookings, ticket prices and available tours
here. 🛳️
Please let us know how you liked the tour once you visited, and which part of the exhibition you enjoyed the most!
Have a nice day,
Sarah