Why use two vmbr's ?
vmbr0 and vmbr1 interfaces can be usefull when you virtualize pfSense/OPNsense, creating a LAN and a WAN.
If you want to just use vm's, one vmbr will do.
I assume Switch 1&2 are managed ? You can configure VLANs in those switches.
For separating VLANs you must use port...