Hi, can a piefed server be run only locally? Not to get any content from other servers?
Local content, local users.
What are the minimum hardware requirements? Like cpu, ram? I understand it can eat more resources based on how much activity it has. But, can i get some examples on how much should or can a intel dedicated machine like 14900k with 64gb ram can handle? Is this software more cpu hungry or more ram needed?

Here's the relevant part from the documentation: https://codeberg.org/rimu/pyfedi/src/branch/main/INSTALL.md

PieFed recommends at least 4GB of RAM and 2 CPU cores and to double that for more than 10 users. And that's with federation enabled. If you don't federate and only have a few local users, I suppose there isn't much to do for the database, so you'll get away with less network and CPU usage.

Not sure about running it locally, but I'm sure someone will chime in. Maybe just set Federation to "Allowlist" and don't put anything in, so nothing is allowed.

There is also a checkbox somewhere in the admin area which controls whether non-admins can add remote communities or not. So potentially admins could add a couple of remote communities and leave it at that.

With no or low federation, even a Raspberry Pi would be fine.