Very impressive, and it's of course quite clear that the OP didn't just walk off the street into Blender HQ. Many years of experience at Unity is probably quite helpful when it comes to knowing the domain. :)

This change [1] was my favorite, optimizing an image processing step by removing lots (and I do mean lots) of table-based "optimizations" and replacing them with just straight up floating point calculation, and making it ~4X faster on the OP's machine. Fantastic!

[1]: https://projects.blender.org/blender/blender/pulls/115801/fi...