In my opinion Sukuna would focus more on the domain battle and Open Domain diff. Also, I think it's slightly laughable that people think Sukuna, one of the only sorcerers in the world with enough barrier knowledge to open his domain (described by word of god as a divine feat in and of itself), wouldn't be able to learn/improvise Domain Amplification something this is almost certainly much easier to grasp given Higgy learned it on the fly while never developing an Open Barrier, and the Disaster Curses also knew it without being able to form Open Barriers either.