Hi faa,
We use a Pfsense router, basically its a desktop computer with two NIC cards where the pfsense software runs.
So, probably one NIC is used as WAN link for Internet access, and the other one connects to the LAN?
If so, you must define two subinterfaces for the LAN-NIC, one for the corporate, and one for the guest VLAN and connect it to a VLAN-trunk port of your "core" switch.
And now that we have 5 switches do we have to create VLAN's in all of them in a similar manner .i.e to have VLAN ID 10 and 20 in each of them..some are 24 ports whereas others 48
It depends ...
In general: Any switch that connects to your router's LAN port [1] or to any of your APs [2], or that interconnects two switches of types [1] or [2] must be VLAN capable and ports must be configured for either trunk port (VLAN 10, VLAN 20), access port (VLAN 10) or access port (VLAN 20).
But you may also use unmanaged switches, for example for your wired PCs connecting to the corporate network: Given, your corporate network is VLAN 10, connect the unmanaged switch to a port of a managed switch, that is configured to be an access port for VLAN 10. Then connect the PCs to the ports of the unmanaged switch. The unmanaged switch can also be a manageable switch left unconfigured (i.e. meaning any port being an access port for VLAN 1) .
For more precise statements, a picture of your topology would be helpful.
PT