kc9udx I use it to copy a large directory tree from one place to another, especially when doing it remotely, as the process might get interrupted. When resuming such a process; it becomes necessary to skip the files that are already copied. So I pax -r -w -v -pe source target
You'll need to add one of -k, or -u, or similar, to skip files; otherwise, it's all copied again (do a ktrace to see this).
kc9udx pax is not network-aware; so it will only do that if you are working with a network mount.
No, but you can combine it with ssh:
$ ssh arpa.sdf.org 'cd bin && pax -wj .' | ssh arpa.sdf.org 'mkdir X; cd X && pax -rjvk -pe'
(which is a very roundabout way to copy some files.)
Of course, you can also use tar instead of pax here.