+1 for Home Assistant… phone app is fine - much safer / simpler / easier than writing anything yourself (but as it’s open source, feel free to contribute if you’re still wanting to get your hands dirty)
If the NAS really will be the heart of the system, ensure you start thinking about how you’ll restore those backups you’ll need to take …
Make some kind of notes / drawings on your setup… it’ll make sense today, less so next month.
Edit: forgot to mention volumio for multiroom audio. But, I’ve had some issues with volumio in general, so, check it out, but don’t feel compelled to stick with it because of my comment…