I’m assuming that you’ll have multiple actors per movie. It’s just a suggestions but if I wanted to add additional information about a relationship I would probably use a repeater field and then use a Post Object field instead of a Relationship filed.
The drawback of doing this is that it would be far more complicated to do a reverse relationship query if you want to show what movies each actor is in on the single actor page.
If you want to use reverse a reverse relationship query the problem could be remedied by adding a acf/save_post filter that takes the actors in the repeater field and puts them into a standard wp meta field with the WP update_post_meta() function.
