https://frontendmasters.com/blog/constructable-stylesheets-and-adoptedstylesheets-one-parse-every-shadow-root/
Constructable Stylesheets and adoptedStyleSheets: One Parse, Every Shadow Root – Frontend Masters...
If you have any shared styles across multiple shadow DOMs (imagine 20 custom button components), a Constructable Stylesheets is just way more efficient.
constructable stylesheets