Well you can easily put your cams on the same network that you already have perhaps add a poe switch for power (unmanaged). That’s with the kit you have. It will work.
If you setup pfSense with a managed switch you can implement vlans, with the cams on their own network, they are a but dodgy with dialling out to their vendor or somewhere. So sticking it on an isolated vlan is generally a good idea.
If your knowledge it not there with pfsense and vlans, stick everything on the same network.