Hi, thank you in advance. So I would like to get a good idea on what would be a good plex build for my home private use, as of now, I am able to do 4K HDR direct play and that's basically what I am targeting but without having my desktop pc up all the time
If you can have a direct stream of 4K HDR without transcoding, this means your TV supports these files. Choosing a NAS in this case will be easy. You could go for budget options like DS118 (single bay) or DS218play (mirror) or DS418 (4 drives/bays).
If you need few extras like Docker/ VM/ Windows Image backup, snapshots etc., then consider plus series models with Celeron inside.
I hope this helps.