The first confguration example is creating the bridge domains where all the members of the domain will be in the same broadcast domain. This is your desired configuration.
But you really cannot control this for only one interface as you ask in your previous post. Broadcast by definition means that it floods to the entire broadcast domain. You can't have a partial broadcast.
The second configuration example is used to add a layer 3 interface into a broadcast domain. This you probably don't need as you are likely using interface configuration on your SRX to create the layer 3 interfaces.
I get the sense that you are trying to use the wrong tool for the job here. Just what network communications issue are you trying to achieve?
It is sounding more likely to me that you don't really want a bridged broadcast domain at all but are trying to use broadcast packets to solve some other issue. Or at least the descriptions are coming off as looking to acheive non-standard network behaviors. And forcing non-standard behaviours usually leads to trouble in the long run.