One thing to add is that I really think the idea of custom spacing values (as Rich describes here: https://richtabor.com/standardizing-theme-json-spacing/) in theme.json that can be applied flexible to a design system is super smart and helpful in my opinion.

I think that somehow I still misunderstand the spacing setting in theme.json a bit, since I see the advantage of custom settings for sure, but I have difficulties with general settings applied (which will be opt-out now, as I understand).

Maybe there should be a more detailed documentation on the settings in the Editor handbook?