Not only have I been a long time Plex user, but I have built a few Plex servers of the years and I wanted to outline my newest setup. It is quite a beast, especially compared to the previous server which was a 2012 Mac Mini which I only used out of simplicity but in the end it was not powerful enough to handle my needs. The form factor was great but when it came to having to transcode anything, it simply failed.
The current build is utilizing an Intel Core i7-8700K CPU with 6 Cores @ 3.70GHz which gives it more than enough processing power for Plex as well as my other Docker containers running on it.
I also opted for 32GB of Corsair Vengeance DDR4 DRAM 3000MHz with Ubuntu server running on a 500GB Samsung 970 EVO Plus Series NVMe drive, originally it was running on a Samsung 860 EVO 500GB SSD but I wanted faster read/write so the NVMe was put in place.
Additionally, I added in Rosewill Gigabit Ethernet Card that is bonded with the onboard NIC with Jumbo frames enabled and a very high MTU which is also reflected on the Synology NAS for maximum throughput. All of this is set up on an ASUS Prime Z370-A II ATX Motherboard.
With the addition of an NVIDIA Quadro P2000 GPU, this setup can handle around 20 transcodes at once with the CPU barely being used. I am hoping this setup will end up lasting quite some time without needing to upgrade it again that way I can simply focus on expanding the disks in the Synology.
And as mentioned to keep the server simply handling Plex and the other docker images the only drives is the NVMe with everything else being stored on the network storage.