I am running a Debian 8 machine that has 50mb/s download and 5mb/s upload(on a good day) connection and I need to remotely upload large video files upwards of 15gb over a Wide Area Network. I am not sure what file transfer protocol would be the fastest and secure. ie SFTP, FTP, FTPS, etc.
That depends on the type of files that you want to upload.
If they are databases or non-compressed dumps, scp is more efficient, if they are compressed, FTP is more eficient, scp more secure.
Often in my internal network I go commando and do tar's on top of netcat's.
If the contents are incremental and always the same files and do not change much over time, a good idea is doing an rsync on top of ssh.