Tabjolt would still be relevant as it can be used for testing the load on the Tableau Server depending on the amount of people interacting with the view at once. This load is entirely handled by the Tableau Server which would not be affected by the data source connections being live vs. extract.
Let me know if you have any other questions or need more clarification. I can reach out to internal resources to get more detailed information if you would like.
Hope this helps!