I want to share limited data with friends. Does zerotier support limited sharing?

I have made a private network where any of my machines can connect to others.
But if I want to make a directory available on a raspberry pi for example, and make files available, is there any way to do this? Or once I add someone to my zerotier network, they can see any computer?

So first question, can I create a network where I just expose a single machine, and then I guess I could give them an account and sftp access which would just give them some files not everything

If they can see all my machines, but have no login, that’s still fairly secure, it’s just weird. Is this use case at all supported by zerotier, or should I be using something else for that?

In this case, I have a friend who is technical but not great with computers. She is curating technical videos and we are writing papers together. I want to give her a place on a huge hard drive where she can back up 1TB of videos, but I don’t want her to mess with my computer accidentally.

As an aside, it’s startling how professors of computer engineering can be terrible at basic document sharing. I’ve been in two ECE departments where files are copied back and forth because the professors are not used to a shared folder, never mind git.