different between using Bridge and not

Hello

I am running a network using RB1100 with multiple vlan’s and different services (PPPoe, Dhcp and Static IP, Hotspot, VOIP) theses Vlan’s assigned to Ethernet (Ether 5 as Local)
The RB 1100 connected with ToughSwitch as Trunk, This Switch connected to other sites using P2P as Bridge, the clients connected to the sectors using UBNT Devices with desired vlan,

Toughswitch Configurations
Port 8 as Trunk P2P
other ports Vlan’s assigned as (Tagged, Unttaged, Exclude) depends on the clients

My Question is,
what’s the different between (assign these multiple Vlan into a bridge and Not by using a physical interface) (i know bridge uses CPU) but we need the benefits between them.
is there any extra configuration if using bridge like (change MTU, MRU …etc)

Thanks