Haven't used Silverblue or Bluefin but the way I've seen it explained is that Bluefin, Aurora, etc include a number of QoL and practicality adjustments that make them nicer/easier to live with as a desktop OS than baseline Silverblue is.

Yes! I used to use Silverblue too. Things like Tailscale, Docker, Davinci Resolve, nvidia drivers, and all codecs are a button-click away or already properly set up for you out of the box on the universal blue projects.