Wiring direction inward vs. outward will not matter because, yes, mapping will take care of it.
For a mapping function, I’d use the one from this thread - I think it was made with LED sets like yours in mind.
I don’t know if the output expander will repeat data if you start multiple channels at index 0. But I have successfully driven multiple sets of identical LEDs from an expander channel simply by connecting multiple data lines to the output. (How well this works is dependent on wire run length and the specific LEDs involved, but it’s worth doing the experiment.)
Any 2D pattern should look good on that display, especially things that are radial to start with.