1. pfSense does not generally support more than one network connection per LAN.
Most off-the-shelf routers have one WAN port (for internet) and multiple LAN ports (for your stuff). You can plug any/all stuff into any/all LAN port(s) and it just works.
pfSense is not like this. It expects to have one WAN port and one LAN port. That's all.
If you want more, you're supposed to use a network switch. This may seem counterintuitive, but switches do everything in hardware and are actually faster.
This means there is really little need to buy a pfSense box or NIC with more than two Ethernet ports (at extra cost). It won't use the extra ports by default; they are NOT plug-and-play. In fact, they won't even work until you set them up!
I wish I'd realized this, as I purchased a pfSense box with six ports, which cost more. I didn't realize the extra ports weren't intended to be plug-and-play for one LAN.
It also means that if you need more than 1 LAN port, you really should invest in a switch as well. This obviously costs in addition to whatever hardware you are purchasing to run pfSense itself.
A. If you have already invested in a multi-plug box and want to use the extra ports, you can use the extra ports via bridging.
B. If you have a managed switch that supports Link Aggregation (LAG or LAGG), you can gang multiple ports on your pfSense box to multiple ports to your switch.
It probably won't speed anything up, but why not? Can't hurt! See here.
C. If you can wrangle multiple subnets, you can assign the extra Ethernet ports to their own subnets.
(If you don't know what that means, don't try.)
Now, a lot of the Qotom boxes (and similar) come with four NIC ports by default, and that's fine. Same for a lot of popular NIC cards. Just don't expect the extra ports to be immediately usable like on a Linksys or Netgear.