Keeping this as a memory for myself.
Objective was to find large files and move them (server-side) to another Google Drive to free up space on the primary one.
Find large files
$ rclone lsf -R --min-size 20M gdrive1:folder > large-files
Put them into one folder from which we will transfer
$ rclone move gdrive1:folder gdrive1:largeFiles --files-from large-files
Move them to gdrive2
$ rclone copy --progress --progress-terminal-title gdrive1:largeFiles gdrive2:folder
Note: you need to set the following line in rclone.config:
server_side_across_configs = true
Now you can delete gdrive1:folder to free up space.