I have updated my setup in the last 2 years.
Starting from Pi4 8b to 2x Pi4 8 GB to Zimaboard 8 GB to a custom i3 12100F NAS.
Running everything in Docker.
Pi4 is not a good option if you want to run a media server, that tiny Broadcom processor can't handle transcoding.
Zimaboard is a good option, since it has intel quick sync for transcoding + you can add an external GPU like Nvidia T600 (i used) or any other low powered card.
At the end, Custom NAS solution is the best if you want to hoard large amount of media + have multiple streams running at a time.
Added images of my setup.
Latest setup running everything smoothly on custom NAS.
View attachment 173305