Well basically I'm reading a list of files from a database, which also contains their names on the remote. The remote can be anything (someone else actually creates the database and defines the remote) but it's probably one of SFTP or Box.
The files are copied under their new name to directories that are also contained in the database or calculated from some other information, and might or might not exist on the remote.
As mentioned in my first post I'm currently using
rclone copyto -v <local file path>/test.txt <remote>:<file path>/othername.txt
on every file, which means that for every file a new connection and authentication has to be made in addition to the copying and renaming, which makes the whole thing last around 10 seconds per file for very small files (less than 1kb) and of course takes longer for large files (up to several Mb but usually less than 100 Mb). There can be lots of files to upload.
I'm using a pretty recent rclone (1.54.x, I think?) on Windows 10.