Low Power Server Build Opinion? - eviltoast

So I currently have a HP Prodesk G4 i5 7th Gen with 32gb RAM running Unraid. It’s used for Plex and AdGuard Home.

I have another unit with the same spec and thinking about giving TrueNAS Scale a true as the UI and Config seems more in line to what I am used to.

It was this video that got me interested: https://youtu.be/KmYV8f-BihQ

Storage will be my issue I don’t have the funds for much so thinking about getting 3 of the following drives (yes I know they are USB but works fine for my unraid setup) in a RaidZ config which I believe will give me 1 drive redundancy: https://amzn.eu/d/bqb10wZ

Was thinking I could find someone to 3D print me a 4 bay toast rack style holder to rest the drives on top of the ProDesk?

The 2 internal drives (256gb M.2 and SATA SSD) I am planning to use as Boot Drives.

Gonna add a decent Apps catalogue too: https://truecharts.org/manual/SCALE/guides/getting-started/

Looking for opinions please, any dos and don’ts. As mentioned budget is tight and looking to keep energy bills down.

What do you all think?