Instead of "headless", which I agree is confusing, perhaps instead: bare-bones; unstyled; fully customisable; extensible; unopinionated (maybe).

"Artisan" seems fine, although it's slightly obscure. Perhaps instead: control-freak; obsessive; perfectionist. They are somewhat negative, but they're also points of pride for some.

So for example: tiptap, the fully customisable editor for website perfectionists.

Just some suggestions :)