On investigation it turns out a few things are different. Native Google Drive folders have custom icons and so osx creates a hidden Icon file within each folder. Furthermore Google Sheets/Docs/etc files have zero file size (somehow) on odrive but are > 0 on native Google Drive.
Bit silly of me this one. I’ve since noticed another folder on odrive’s version which doesn’t exist on the native google drive sync. It’s the shared with me folder. It’s large and accounts for most of the disparity.
Thanks for the help and the chance to brainstorm!