Nothing definite because no one really knows how iCloud Drive works. But it sure seems like iCloud Drive is designed for an earlier generation of connection speed and computer speed so that it runs everything in the background as a low priority process.
ever since Sonoma 14.5 iCloud Drive is now a File Provider and that seemed to help quite a bit. But I still don’t trust it. I’m using 25 GB of sync.com for $12/year.