I am running plex server on a low power i3-7xxx. thanks to the igpu that thing can handle a few 1080p transcodes at once. Even 4K HDR transcoding is possible, though I never get more than one or two of them at the same time. Unless you need it to encode subtitles into the video or you have many simultaneous HDR to SDR conversions going at once any cheap old PC with an intel 7th gen or newer and igpu should do well. Oh, and I don’t think they can handle AV1, but that is still very uncommon.

WinSCP for editing server config

Rsync for manual transfers over slow connections

ZFS send/receive for what it was meant for

Samba for everything else that involves mounting on clients or other servers.