Thanks for the long thread full of pictures and explanations! I swear it has been more informative that some dedicated NAS-related tutorials and guides I've read/watched recently.
The thing is that I'm thinking of building a RP4 based NAS for when I'll be able to get some real estate in Greece for the holidays, and as far as there are travel restrictions, I figured I'd study thoroughly everything I want to have/do there, and a NAS integrated to a smart home network is one of these things.
Once again, thank you for all of that precious information!