I would like to go for 1 license. Let me know if there is any solution to combining data from different accounts at a single place. Anyways, I would like to store all the data into a single bucket.

One question as well:
Does this product also perform backup of different versions of files in Onedrive?

As a O365 Home subscriber, I manage 6 users.
But the data itself is distributed across three onedrive accounts - 400GB approximately per account.

I was under the impression that I can add multiple onedrive accounts for backup to S3.

Please ignore previous reply and reply to the below mentioned comment.

Thanks for the reply.
Can you confirm or answer below mentioned points?
1. Multiple onedrive accounts can be backed up to AWS S3 for a single user license
2. Are there any limits on the size of data transfer? The first transfer would be around 1.2 TB and later it would be down to just a few GBs.
3. Does your product perform incremental backups after the first backup?