You probably don’t need 2 NUC’s - here’s an alternative idea:
Get a NUC, and get Proxmox onto the NUC, and then you can get the “appliance like experience" running a HAOS VM under Proxmox, you can also get all kinds of different containers.
… the same thread mentioned tteck’s work, which I have to say is quite impressive. Things you want to achieve but not (yet) available as an add-on in HAOS, you likely find something useful among tteck’s scripts.
Proxmox Helper Scripts | Proxmox Scripts For Home Automation (tteck.github.io)
Not for everyone I know, but if I’m in your shoes I probably would (force myself to learn Proxmox and) go this route.