You can ocntrol everything from any browser in your network, just type „max2play/“ in the URL.
You can use the full scope of the Squeezebox system. Therein, a lot of plugins for multiroom audio use are included. Radio is no problem as are creating playlists and editing them.
A quick search gave me a possible solution for soundCloud, but he have not tested it yet: https://github.com/danielvijge/SqueezeCloud