Have you read the sidebar and rules? (Please do)

Yes!

What is your intended use for this build? The more details the better.

I'm looking to get suggestions for building (myself) a NAS or a mini PC / external drive combo for several various purposes.

• I'm open to various form factors such as a NAS or a mini PC with an external multi-drive bay attached. I'm open to building a NAS of my own to save money.
• File server for central storage of my media
• Plex server (typical max usage would be two 4K streams and a 1080p stream, sometimes the streams are transcoded)
• *arr media management
• Home Assistant server: I have what's probably a fairly average installation, but in the future, I'd be interested in installing something like Frigate for person and object detection in cam streams, which I know is resource intensive.
• Immich server: I would continue to do my photo editing on a different machine, so it's likely the photos themselves would remain on that other machine unless the file sharing aspect is performant enough for me to have the photos on this new build and Lightroom installed on my other machine. Between the two, my preference would be to have all my media on the new machine. After playing around with Immich on my main machine, I discovered it can be fairly resource intensive, as well.
• Backblaze: I use Backblaze to back up everything on my current machine, and it would be great if I could transfer that instead to this new machine.

If gaming, what kind of performance are you looking for? (Screen resolution, framerate, game settings)

No gaming planned for this system.

What is your budget (ballpark is okay)?

Ballpark of $500, but if that's not possible, then it is what it is. I don't currently need more hard drives, so those would be excluded.

In what country are you purchasing your parts?

U.S.

Post a draft of your potential build here (specific parts please). Consider formatting your parts list. Don't ask to be spoonfed a build (read the rules!).

I don’t have a specific parts list yet, as I'm not sure yet what type of system would be best. I’m open to all suggestions, whether it’s for a full DIY NAS setup, a pre-built mini PC to expand upon, or other creative solutions. Nor am I looking for someone to provide a parts list for me at this point.

Provide any additional details you wish below.

• For Plex: I’d prefer to enable hardware transcoding, so any recommendations should consider this.
• I’d like support for several drives, either internally or via external bays, to accommodate my media library. I currently have 5 3.5" HDDs that I would move to the new system.
• Noise isn't a huge concern but quieter and especially power efficient solutions are a plus.
• I'm an advanced intermediate computer tinkerer. For context, I've wiped a Mac Mini and installed Proxmox on it with Home Assistant and Linux Mint VMs - but I struggled through a lot of that, especially file sharing permissions to connect the Linux VM to my main machine. I don't need things to be baby-proofed, but ease of use is a big plus. If I have to rely on Linux terminal commands to complete a lot of the setup, I'm going to have a bad time. It's for these reasons that I've been considering something like a Beelink mini PC, but I haven't been able to determine if it would fulfill all the requirements I listed above.
• This new system and my main one would be connected to my home network via 1G Ethernet.