I run an Unraid server with a X470 motherboard and Ryzen 2400G. Got some old drives in there plus 3x WD Reds for main storage. A M2 WD Blue takes care of the cache drive element. Works great as a NAS, Plex works great in a Docker container - as do Pi-Hole and many other useful Dockers. It runs 24x7 with Shinobi in a Docker as well.
If you want even cheaper, a B450 motherboard would do the job but I wanted more 'on the motherboard' SATA ports.
The good thing about Unraid is the ease at which you can grow the array should you want to. Not sure how it would do in terms of handling loads of Plex clients at once, but streaming to one client is absolutely fine
Unraid has gone through several generations since the logic ‘get as many SATA ports as possible’ applied, 8-10 years ago everyone would have agreed, now, not so much.
Now people understand indirect cost and efficiency are important (power/heat/noise), we have access to 10-12TB drives at reasonable costs per TB, running 24 bay monsters is less and less popular, except in quite niche situations. Most people don’t need 288TB RAW + NVMe cache pools, those that do realistically probably want PB’s rather that TB’s. Point being it’s better for a variety of reasons to replace small inefficient drives with larger ones, save the power/heat/noise/space etc. Also £20 buys you a decent HBA for 8 drives, if the upgrade cost between boards is significantly greater than that, it’s a waste of money in this usage scenario, also drives keep getting bigger and cheaper, so again you buy the best £/TB over time.
Then people realised that rather than buy drives, have to fit them in cases and power them, deal with failure/RMA’s etc. for less than the cost of buying one drive, you could locally mount inexpensive cloud storage and have non of the issues. This the hybrid storage set-up was born. Now if you had a reasonably quick connection, you could have fast local storage and offsite backup or shove the files that you only used once in a while and were easily replaceable in the cloud. Heck if you were paranoid, you could even encrypt them.
The next step after that was obvious, if the storage is in the cloud, why isn’t the server? It’s inexpensive, you know how to run your server to ensure direct play, and having a symmetrical gigabit connection to your storage means 100MB/s transfers, no purchase/depreciation/power/heat/noise. After that sinks in, it’s largely game over for large local as a model unless you have awful an awful local connection or a very specific need for local storage/specific hardware.
As to the Plex point, its as capable as any other docker based/bare metal solution running on the same hardware/CPU/GPU. Direct streams are not CPU limited. Most home users in the UK are barely able to get 20Mbit up, they’ll run out of uplink before anything else unless they make a really poor media/CPU choice and need to transcode or do something stupid involving H265/4K + HDR. The exception is Windows, where if the user has a PlexPass they can use HWDecode out of the box with a suitable intel iGPU or Nvidia GPU, other OS’s still class it as experimental, so you only get HWEncode unless you want to enable it, but all of that requires a PlexPass (or JellyFin).
