The wireless tab is for wifi hardware in the pfSense box, yes.
It depends what the Fritzbox can do. If you can set that up to use a VLAN directly that traffic will probably pass your unmanaged switch and you can then connect to it using a VLAN interface in pfSense.
You could do something even more unconventional like setup a tunnel of some sort between the Fritzbox and pfSence to separate the traffic that way. A VPN if it can do that or even PPPoE can work.
A managed switch is a better way to do it but it depends how much you want to save money or like playing with network config. 😉
Steve