Can I boot from an external drive with hardware encryption? Can I boot from an external drive with hardware encryption? 

For example I can add a password to my Samsung T5 that turns on the drive’s hardware encryption. Can I boot from that, as long as I know the password? (I assume yes, but that I’ve got to install Samsung software on the target machine first.)

Is the answer any different if I additionally enable FileVault on the external drive (APFS, GUID)?
I don't think so, because the drive can't be unencrypted by the Mac before an OS is loaded. 

If you want to encrypt your data, then using FileVault is the best way, and your Mac knows how to boot from a FileVault drive. 

However, it will boot to Recovery first, then ask you for the drive's password, then let you boot up.