sftp is using the SSH protocol, you should have mentioned that.
scp is an old way to use the SSH protocol to transfer files and is obsolete and should not be used. Also, I didn't understand the comment about "used after you ssh" - you most definitely can use scp from your local machine to a remote one.
ssh is not actually a file transfer command, though it can be used with pipes so we often pipe data from a file on one side to pipe it out to a file on the outer side - but more context would have been appreciated. If you mention SSH then nc would probably have been worth mentioning as well.
if you've mentioned ftp, then other "clients" are probably worth mentioning, such a curl and wget - both do anything that ftp does and more.
Lastly, there's a bunch of new stuff that is useful: croc and magic wormhole might be worth mentioning.
Eh. Nitpicking:
Lastly, there's a bunch of new stuff that is useful: croc and magic wormhole might be worth mentioning.
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Can't wait for your content:)