Do you know anything about the 20k file limit going away?I've have never experienced the OneDrive being slow, I sync between 4 machines on a regular bases and my Project Folder gets multiple changes at least once an hour all throughout the workday, these can range from a few MB to hundreds of MBs.
OneDrive does run asynchronously were Dropbox tends to run synchronously.
They will be updating OneDrive to use the OneDrive for Business Engine in Windows 10 with updates scheduled for October and something to replace placeholders by December.