Nginx can be used as a reverse proxy for S3 compatible storage and buckets. This is useful in many scenarios, including adding authentication, security or custom routing to S3-compatible solutions. 

Use Cloudflare as CDN. However, To handle large size files, Wasabi's S3 storage service is best. you can turn Wasabi into a CDN with CloudFlare cost-effective.

Wasabi is a hot cloud storage service that provides object storage services. use CORS and custom domains to Wasabi S3 bucket using Cloudflare. Wasabi guide