@ncw : Thanks for your detailed response. We will keep our upload response stable by adding new details without modifying the existing content. We will include the newly added information in our document for better understanding. So you can proceed with the changes if they work as expected.
How many parallel upload APIs will be triggered for a single user? As you mentioned, we will throttle requests if we get bulk requests in a short period. So, Limiting the number of parallel uploads to <=5 will be the better option. The requests will not be throttled in this case. We can upload more files than the throttled approach.
We will try the beta version and share our feedback.
The default number of simultaneous transfers with rclone is 4. This can be changed by the user using the --transfers flag, however we've found 4 to be a nice compromise for most providers and it sounds like it will work for you.
The test I did was excessive uploading very many small files at once. I think the typical rclone user won't hit the upload throttle limit at all.
Let me know your conclusions on the beta.
Note that if you use the flags -vv --dump headers you can see the HTTP transactions rclone is doing which may help you figure things out.