If I could weigh in with my 2 cents on Vader’s Castle in the opening scene. If the goal is to clearly establish the scene as being set on Mustafar, I don’t think including that shot is warranted. I believe that if the ‘Vader’s helmet’ scene is moved up to the start of the film, along with new volcanic establishing shots, people who are familiar with previous films would easily discern the planet on which the scene is set. I reckon that showing Vader’s Castle would come off as “hand-holding”. Not only that, it would be an establishing shot for a place that isn’t where the scene is actually set and might actually be confusing in different way.
Sorry if some of these points have already been covered here. Still, I feel using Vader’s castle isn’t the best choice here… and yes, I’m a sucker for canon, so I felt extra incentivized to share my thoughts on this.
There’s my two pennies, spend 'em how you will.