I have a similar setup except I'm using Jellyfin instead of Plex.
For hardware, it's a Ryzen 5900X, 128 GB of memory, 1 cheap SSD for the OS, 2 1TB NVME drives for fast storage, 2 2TB SSDs for normal storage, and 4 20 TB drives for bulk storage. 1 cheap GeForce GT 710 for video, and 1 Nvidia T1000 for transcoding.
For OS, I'm using Proxmox. I have a few VMs, but mostly everything lives in LXC containers.
For the NAS part, I have the hard drives mounted as a raidz2 on the Proxmox host, and I pass access through using LXC Bind Mounts. The pair of SSDs are in a mirror, and same with the pair of NVME. Game servers live on the NVME, and everything else on the SSD.
Game servers that run on linux run in LXC, otherwise I have a windows VM. I've never liked running game servers in Docker.
I also have Proxmox Backup Server running on the Proxmox host itself.