Just thought I would post my setup that currently runs great for Plex.
Intel i7 13700k - Overkill for plex - just make sure yours has igpu for transcoding.
ASUS PRIME Z690-A
128gb DDR5
Synology NAS - 20 terabytes - with 10gigabit over fiber. Stores all TV/Movie media
The Synology and Unraid server are in different locations (house/detached garage) and serve as duplication for most data and backups.
If you will only be running plex you don't need latest CPU, mb, etc.
Hope it helps.