I’d DIY it, so all on one device. I use an old PC (way overkill) and added some drives, and it does everything I need.
Probably? I don’t know much about it, I just use a regular server distro. As long as it gives you enough control to run docker/podman or bare metal services, you should be fine.
If your network between the NAS and mini-PC is fast enough, it should work to seed over the network.
AlmightyDoorman