Fascinating video, thanks Alexander! I feel vindicated. 👍
Glad you enjoyed. I find it a fascinating topic. It's one of my favourite piano interviews of all time in that channel, there so much golden information in there with some funny moments too.
Since I am just a hobbyist self teaching I wondered about these things as I went through my journey before that video came out, I am glad it did, a lot of the stuff confirmed at least what I already thought and learned elsewhere. Ultimately, there is a lot more what makes an action feel light or heavy besides measuring with a bunch of coins however, and upweights are rarely discussed, which is another contributor how an an action feels. Most digital pianos the upweight is far higher than acoustics, that can contribute to fatigue when sustaining notes ( I suspect). The Casio I own has an upweight close to downweight, OTOH, the kawai is much more reasonable in that respect and more representative of a typical acoustic .
I didn't find the NWX in 645 too bad at all mind you, but the new grandtouch a step too far for me with the 675 being the worst offender of the lot. A lot of reasoning went into why I picked the kawai in the end of the day, and not a yamaha for my daily praccy, it wasn't for the sound, but the action, but it wasn't an easy choice, The Roland PHA-50 action was also a contender at the time, but the kawai won for various reasons.
For me, years of typing, starting on those heavy dumb terminals have taken their toll over time. Sometimes I would feel it in my fingers with the Casio. Even though the kawai does have a heavier action than my previous Casio, I've had no issues with it whatsoever. The occasional pain I would get I've never experienced again with the Kawai. I also saw a teacher few times just to check I wasn't doing anything horrendously wrong with technique and posture, but she was very happy with my progress, apart from some minor suggestions which I incorporated since.
I also learned a lot from sports when I was younger about the benefits of low resistance training with faster repetition on bikes, versus higher resistance with lower repetition rates, the latter gave me knee problems at the time, which the former approach solved nicely. Learning from that, I am not a firm believer in the benefit of overly heavy actions, just for the sake of it, with the believe you'll gain strength more quickly versus getting injured.
I think with your experience you'll enjoy the kawai a lot ... I hope , I'd love to hear your feedback when you do get it.