Two Nextcloud instances for security?

Hi, finally setting up Nextcloud in an effort to de-Google myself and replace GDrive for good.

I am currently running Nextcloud via Tailscale and that works fine except for when i want to share a file to someone outside of my Tailnet. I have heard of federated Nextcloud but i am not sure that i quite understood the purpose of this or maybe there is a better solution? If i run two instances like that, will i simply be able to share certain files over to that instance for sharing?