I have found that you generally get best speeds to OneDrive with the default parameters. You may sometimes get better performance if you have checkers=16 (for a short while). You can see more details in this post:
You really need to have a special situation to start tweaking the parameters (like the number of transfers).
What are the characteristics of your data? How many folders? How many files in each? Typical file size? Total size? How many of the folders and files are already present in the target (to be checked and then skipped)?