v11 to v12 - object storage changes?

[lando_uk]

Hi,
I need to finally bite the bullet and upgrade to v12. I read there's some changes on how s3 object storage is processed but can't find any specific details.
So my current setup is pretty standard, it's using a SOBR to immutable S3 - Is there anything i need to be aware of when upgrading? Will it use more space, will it cost more in API calls, does it take hours to convert anything?

Any gotcha's or do i just go through the upgrade wizard as normal?

Cheers

[lando_uk]

To add, I have upgraded our test veeam to 12.1.2.172 and that went fine, but that doesn't have 40TB of S3 attached, hence the question.