--drive-upload-cutoff
Cutoff for switching to chunked upload.
Properties:
Config: upload_cutoff
Env Var: RCLONE_DRIVE_UPLOAD_CUTOFF
Type: SizeSuffix
Default: 8Mi
So any file bigger than 8Mi by default changes from a single upload to uploading in chunks. The debug logs should the chunked uploads.
Streaming cutoff is for unknown files sizes and a global flag so it's somewhat dependent on the remote.
--streaming-upload-cutoff SizeSuffix Cutoff for switching to chunked upload if file size is unknown, upload starts after reaching cutoff or when file ends (default 100Ki)
You'd see that also in the debug logs. I think some remotes that can't give a file size would use that but I can't think of any offhand as I only use a few remotes myself.