I run a similar setup, but with syncthing as the syncing system. Every time I connect the phone to the charger it just syncs the database and I can even sync it outside the home network. Works like a charm. Worst case you get a sync conflict which is easy to solve.

I use them as well. Cheap, reliable and easy to use. I only had trouble once, where I was caught in some sort of anti-spam measure and they blocked my account. An email to their support fixed the problem pretty quickly though.

One thing to look out for is to determine where you want your backups. You can’t change your account’s server location after you create your account afaik.

Might be a slightly unpopular opinion, but Volumio (software for a raspberry pi to run it as a headless audio system). It’s good, it’s relatively well maintained and works. But paying 7,50 a month for this software to get multiroom audio, Tidal integration and some other stuff is ridiculously expensive. That’s nearly 90 euro a year and the only thing that is actually an addition server side is syncing settings across devices and the Tidal integration (requires license fees iirc).

And sure, I can’t buy multiroom speakers for that kind of money, but damn, is it expensive.