not sure your use case, but it seems that api calls/costs are a concern.
i use cloud storage mostly for backup. veeam backup files and other stuff.
i use a combination of:
- wasabi, a s3 clone, for hot storage. $6.00/TB/month. no charge for api and downloads.
- aws s3 deep glacier, for cold storage at $1.00/TB/month
if that sounds interesting, check out this post.
where i have an identical source and dest with 1,000,000 files. wasabi tooks 33 seconds to sync.
https://forum.rclone.org/t/fastest-way-to-check-for-changes-in-2-5-million-files/25957/11?u=asdffdsa