It provides all the tools we need for your on-page SEO. From easy implementation of 301 redirects, to declaring canonical urls, and the usual SEO meta titles and descriptions, it provides more options than most other website builders
Plus the Designer user interface allows for declaration of html selectors and custom code when required.
Like any website, it is extendable for things like technical SEO. If you know what you're doing then adding structured data / schema for things like service types, products, organisation schema, local business schema, FAQspage, reviews and article or blogpost schema is relatively straightforward.
Finally, Webflow sites load quickly. They use the fastest CDN in the world and are backed by a global infrastructure.
The only caveat to page load speed is that Webflow is only as good as the developer who builds the website. Using large images, too many fonts, loading background images, having html, CSS and JS bloat and loading unnecessary 3rd party scripts all have an impact on page load speed so ensure your developer understands all of this.