Node-RED <> node.js
Node-RED is a graphical logic software, that has alot of plugins and also some KNX plugins. The KNX plugin communicates with the IP router/interface to exchange data with the bus, no BAOS needed.
There are alot of different projects to build own KNX connected devices, which is not hard to do at all, but these devices don’t integrate with ETS for configuration, as you need an expensive license from KNX.org for that.
Sorry I have no idea about ABB fancoil modules, only regular floorheating here, which is very simple to integrate. I even skipped room contollers and only set the heating temperatures of the different rooms with Homeserver QuadClient, as you do not change this very often at all.
My air conditioning devices don’t have any KNX interfaces but WLAN and are integrated in ioBroker, which is connected to KNX with Node-RED.