I’ve only watched the first video where you make and import a chair, but in that 12 minutes, it solved several headaches I’ve had for years.
I never had someone point out to me that the default blender cube is 2 meters tall and is a good stand in for scale at a glance.
I didn’t know that Unity orients to -y, that is not the direction I would have guessed.
Selecting the faces to move the 3D cursor to adjust the pivot to the ground is the smartest way to change the pivot that I’ve seen, and fighting with pivots in Blender and Unity has been a nightmare for years for me. And learning the dropdown for ‘center’ or ‘pivot,’ will be an important distinction from time to time; I can already think of a few times where it would have helped me to know that, so I’m glad to know it now.
And I surely didn’t know the housekeeping of making sure you don’t import your Blender camera and lights, which sounds obvious but now it’s explicit and I’m sure that would have added stress and frustration later on if I had to learn that one by mistaking it 
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