In terms of network, your Connect is currently establishing Sonosnet and all streaming content will go through it to the rest of your speakers.  Any wired speaker can do this function, not just your Connect.  However, you can also operate your system in ‘wireless’ mode, with each speaker connected to your router over your routers Wifi. This really doesn’t have anything to do with adding in the playbar, as you can operate in wireless mode with or without the playbar.  

The term ‘master’ though, is often thought of as which speaker/room is getting the music stream and sharing it with other rooms when grouped.  That really depends on how the request to play music is made and varies with each request.

Is it really a Sonos Connect? Form your description it sounds more like you where using a Sonos Boost (or its predecessor the Bridge) to start a Sonosnet. Cable connecting a speaker will also result in all speakers switching to Sonosnet. If you where using a Sonos Bridge before: it is known to fail giving connection issues, so you could either cable connect a speaker or switch the system to wifi.