If you run the web extension on the core then yes you would use it’s ip address plus the port for the interface. Try out the web UI before deciding its pretty good but the library bit is a bit clunky. Just follow the instructions in the tinkering section. I tried it on diet pi but found their version of chromium to be too old and it had some odd behaviour I couldn’t work out how to fix so went back to Ropieee… If you ok with Linux then it’s worth a punt.
RoPieee is very good at what it does though and makes the most of the display and gives you playback controls, i did ask for library feature like the one in the web gui as a feature request. If enough people also request it the Dev might add it in. It’s a a lot simpler to setup and maintain then any other music oriented pi distro I have used.