I've read that you can use the OneDrive sync client with Windows 365. If so, would this be like have a LAN connection to SharePoint Online (as it's staying inside the data centre) and could we expect much faster sync speeds than with a conventional client. I.e. would it be possible to work with very large files stored in SharePoint as if they were local files?
Overall it would be the same experience when using OneDrive for Business from a physical PC. Simply sign into the OneDrive for Business client and it will add a node in File Explorer, enable KFM (Known folder move) to sync your desktop, documents, and photos to OneDrive and across your devices.
Cloud PC's do have a fast connection to the internet which has been highlighted in a few of our Mechanics video's, but there is no "special sauce" that we've implemented above and beyond the native experience which is same to a physical PC with OneDrive for Business enabled having a fast internet connection.