My guess for your situation would be that the best option is to get a Pi SATA hat and use that as your NAS. Then use the laptop for messing about with game servers, etc so your Pi NAS data isn't threatened by the inevitable screw ups.

The second best option could be to get a SATA card for your laptop and use that as a single server PC. But be sure to backup your data and avoid putting critical functions on this.

Or sell what you have to put money towards an old cheap PC to give a more straightforward setup to learn on. Depends on how proficient you are with these operating systems (learning a new system vs learning to navigate around unusual hardware combinations). I was a complete noob and wanted to make use of my little Linux familiarity and didn't need anything TrueNAS or Unraid offered, so I went with a secondhand mini PC with Debian.