first, with your current setup, i would change --vfs-cache-mode writes to --vfs-cache-mode full
i suggested that today to another forum member and that solved the speed issue.
yes, rclone will cache whatever you point the mount to.
/usr/bin/rclone mount smbdrive: /mnt/smbdrive
or
/usr/bin/rclone mount /mnt/share /mnt/smbdrive