Suggestions about platform to develop a customizable B2B marketplace

I'm starting as CTO with a mission of building a B2B marketplace company from scratch. My original background is not in e-commerce, so I'm researching the best platforms/frameworks that can allow me to build a highly customizable product (features, storefronts, analytical screens, etc.), taking advantage of well-known e-commerce abstractions without reinventing the wheel.

I want to decouple as much as possible the backend and frontend, and one of my few requirements is to use React Native to build a multi-platform mobile-first marketplace. High customization is also necessary, as we plan to integrate with plenty of proprietary features and ML models.

I found the concept of headless e-commerce well-suitable for the case. It leads me to players such as Shopify Plus, bigCommerce, Swell, and Medusa JS. However, Shopify Plus seems expensive for an early-stage venture and also not soo customizable. I like the Mesuda JS approach, but it is not a battle-tested project to bet as a core to my business.

Any opinions or recommendations?