Some other design elements that stand out to me:

- The transition between dropdowns in the top nav. Really smooth, and something you won't see anywhere else.

- Semi-consistent and sufficiently different color schemes for the different products. See the difference between https://stripe.com/atlas and https://stripe.com/us/sigma.

- Subtle box shadows. They've done this by cranking the blur way up around 30px. For comparison, the Google search bar uses a blur around 1px or 2px.