I just recently started my journey setting up Plex with *Arr and have had a blast. I have the setup running on a raspberry Pi. Before I start buying a bunch of external hard drives, I went searching for some dedicated server hardware to comparison shop. Am I crazy to consider buying an old tower server for this, or will a raspberry Pi work just fine for this purpose? I don’t have that much experience but I do enjoy a good challenge.
I think in your case it really comes down to transcoding the streams. If your player doesn’t support a video format, the Plex server will have to transcode it into a format that’s viewable. A pi might not be able to handle multiple transcodes at a time.
I personally use a Synology nas for my server and haven’t had any issues, but can be expensive.