@gumbo2k I am not expert so I cannot give you an answer for sure but I would not disable the sr.scan completely, I feel like that could cause problems at some point.
Anyway, I don't think touching the scan is necessary anymore.
Vates has release many new updates for both XOA and xcp-ng and now the scan is very fast.
If you haven't done already I would suggest to upgrade your xcp-ng and re-test because now everything run smoothly and fast.
Different use cases: Ceph is better with more hosts (at least 6 or 7 minimum) while XOSTOR is better between 3 to 7/8.
We might have better Ceph support in the future for large clusters.