Switching

Dear all regarding this subject im not sure about when using each encapsulation.

Consider both followin configs:

#####################this config:
  ae9 {
        flexible-vlan-tagging;
        encapsulation flexible-ethernet-services;
        unit 2 {
            encapsulation vlan-bridge;
            vlan-id 2;
        }
        unit 3 {
            encapsulation vlan-bridge;
            vlan-id 3;
        }
      
    }
######################is the same?
 ae9 {
	encapsulation extended-vlan-bridge;
	flexible-vlan-tagging;
	unit 2 {
	     vlan-id 2;
	}
	unit 3 {
	     vlan-id 3;
	}
     }

 what i understand is that using flexible-ethernet-service, i will be able to use different encapsulations for each logic units, instead extended-vlan-bridge is applied to all logical units, Im right?

Im planning to set the same config on two or more interface and then bind them in the same bridge-domain with an irb interface, so ....
Can I use any of the previous configs ? wich is better?

btw , currently im running several routing instances

I know I should declare the irb interfaces inside the routing instances where they are going to work, but what about the bride-domains ? should be declared in the same routing instance or can be declared global? 

Thanks,

Leo.