Hello there !
Recently heard about Volumio, I’m a long-time Mopidy user but nowadays I’m mainly using YT music as a streaming service and it doesn’t integrate really well in Iris, plus the YTMusic plugin is almost deprecated.
I’ll have some questions about Volumio, the multiroom premium features and snapcast coexistence.
And most importantly, the WAF is way better with Volumio than Iris-Mopidy 
See you soon !