Do not underestimate the workload; it is intense. How intense will depend in part on the student and the teachers. They operative part of IB Theatre Arts is IB, so don’t expect it to be a piece of cake.
There is research and writing involved, which count more in the assessment than the performance. The writing won’t be as heavy as English, but still substantial.
No AO who knows IB will view IB Theatre Arts as an lightweight course, if that’s your concern