This is a late reply, though it's one that's been stuck in my mind since reading this post. I am doing my best to follow guidance and best practices, but I continually get stuck on one thing: What about sites that need to implement strict look and feel standards?

For example, what about an artistic theme with sharp angles that shouldn't have rounded buttons? This isn't just about theme author preference, as many sites have brand guides or other visual standards that may mean certain editor features or settings should never be used. To stick with rounded buttons, what about a brand that has a precise rounded corner for all buttons?

It seems like blocks should be the perfect way to build a site with preset visual components, but the user-facing settings and controls that often can't be disabled (drop cap and border radius being two good examples) give every content editor the ability to easily break component guidelines.

(Block Styles and Block Variations are awesome features for enabling easier/better ways of cohesively rolling providing alternate styles that exist within a set of visual guidelines. For instance, Default Button and Rounded Button.)

With Global Styles, will theme authors be able to globally set styles and disable user-facing settings to override those styles? Without that ability, I have a hard time seeing how theme authors building sites that implement brand standards have any choice but to constantly fight off and attempt to disable the editor in order to implement a consistent look and feel for their site. At least that's been my experience over the past two years and by far my biggest frustration with the block editor. I hope this can be useful feedback and food for thought.