It really depends on what you‘re trying to do and what your skillset is.

But if you go information architecture first and have that codified in some way (espescially if you already have the templates), then you can nudge any agent to go straight into CSS and it will produce something reasonable.

Have you tried stitch.withgoogle.com?

I created some decent prototypes with stitch but I don't know how it compares to claude design

Google Stitch