Same problem with a Toshiba S70 laptop. Exact troubleshooting as you and I still have the same issue. I've basically run out of options. You are not alone.
The only thing I did that made a big difference (But not solve) was that I created an exception in Windows Defender to EXCLUDE my OneDrive. When that worked, I ended up disabling it all together. Now the 100% disk usage stops after about 5 minutes and stays down which is probably more normal.
My next step will be to disable syncing all folders from my OneDrive account and switch to Dropbox.
The weird thing is that I have three other Win 10 Desktop computers that all work great under Win 10. No issues at all. So this issue is only happening with using my laptop.