hello and welcome to the forum,
is this a one time sync or to be run on a schedule?
assuming reoccurring syncs, once the first sync is done, for each additional sync, how many files would need to be synced?
for the first sync, this might help
https://rclone.org/docs/#no-check-dest
one option is to write a script, as shown in this post
https://forum.rclone.org/t/efficiently-update-copy-only-very-few-files-to-google-drive/23276/7