Hi! I’m Tai and I’m the sole engineer on this project.
Sorry for the lack of response — we are actively working on this feature to iron out as many bugs and polishing as much as we can. We have a few alpha testers providing feedback and helping to find issues before we release 
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Regarding your post:
The only styling exception might be for adjusting the REM size. Will we have an option to adjust this without embedding code on each page specifically for the REM setting? Missing this would be a significant oversight, especially given the significant advancements being made in enhancing the platform’s styling capabilities.
Do you mean being able to set a REM value on a :root selector? If so, at this moment we’re not introducing this capability in this feature set, as the focus is more on expanded access to css properties and values. This is a great point though, and an extremely common workflow in web development.
That said, my team and I are tracking this ticket to see how we could introduce a way to set CSS on the root selector in a future enhancement, for the time being, we’ll have to keep using custom code embedding to set the base REM.
Regarding using flexible values in variables and CSS functions like calc/clamp, you will be able to use css variables in the these values (e.g. clamp(var(--base-font), 1.5rem, 1.5rem)).
Hope that answers your question, let me know if you need further clarification!