In my testing, OneDrive for Business tends to throttle uploads pretty severely sometimes. They request that connections be paused for 120 S at a time, which we do respect. However, I was able to upload at about 700 GBs worth of data quite reasonably across a 75 Mbps UL symmetric FIOS connection.
Also, this will reduce the error messages returned in the UI and show proper throttling indicators on the bandwidth bar:
.957
* [Issue #27541] Fixed handling HTTP throttling responses (429) from OneDrive for Business.