Don’t use an SSD for backup. SSDs fail instantly with no prospect of data recovery. You can use an SSD as your primary drive for speed, but make sure your backups are automated and going to an array of actual platters.
The external drive is HDD, it’s just slow and a bit noisy. I prolly should spring for a new one that might(?) benefit from a USB-C 3.1 connection. I’m not sure the present external backup HDD would...