This reminds me of my teen days with B&W film when I use to make prints, not that I was great at it or anything like that. The tools have changed but, as always, in the hands of a skilled/talented photographer, tools can make amazing photographs! Great presentation!
John, at 1.54 minutes the background mask was foiled by the model's fly away hair on her right side. If you had increased the tone of the background by a large amount ,the mask's shortcomings would have been very noticeable.
Layers is a feature LR initially took over from C1, which had it available since long. That said, C1 'AI' masking is less automated than in LR, but works fine. Colour science is better in C1, though still a little behind DaVinci Resolve (which is motion picture editing only) imho.