Hard and Soft Edges in Maya and How to Get a Perfect Normal Map Bake
Here's the write-up on normal maps that I mentioned in the video:
https://www.artstation.com/blogs/typhen/GMyG/this-is-normal-1-what-normal-maps-are-and-how-they-work
The part I talk about in the video is on part 2 of that document, under the section called "Bake Seams"
Also, I realized after recording that I never went back to the Harden/Soften edge tool. All it does is automatically harden or soften edges based on an angle threshold, which you can set manually, or leave at the default 30 degrees.