Don't underestimate the power of method 2.
A lot of people starting out with projection mapping tend to think that getting the mapping right is the most important part of a show. Correctly lining up the output is new to them, so getting this right naturally gets most of the attention.
I would argue that the mapping is just the tiny final step at the end, where you tweak a few corner points to make sure everything lines up.
When you know that you will projecting on 7 rectangular shapes, you can start creating videos that roughly take these shapes into account. You don't need to know exactly where the shapes are, just how many and roughly what shape they have. By working with a template like the image I attached, you can create all your custom content before hand. You can make videos where you are tracing the outlines, filling the boxes one by one with different colors, fill them with liquid or balls, anything you can imagine.
Then when you arrive at the venue, all you need to do is create 7 slices that take the areas of your template as input, align them, and all your content will work seamlessly.
