In my case I do backup from C and D to E, but temp folder is on C. So it’s not effective.
You can change the tempdir location by using one of the advanced settings. And I also believe there is an option that uses move in stead of copy if temp and final disk are the same.
Kenneth described what you can do and how it works: How can I speed up local backups?
Yes, I changed. But I think that D2 have to be smarter and a rare user have to use advanced options very rarely.