If i were to use a single NIC pc to run pfSense and run that into port 1 and WAN into port 2 of a managed switch and other VLANS in ports 3 + will I take any speed hits compared to a pc with multiple NICs and passing that into port 1 of the managed switch ???
Yes. In a VLAN trunk, all VLANs share the bandwidth of the logical link. In this case, the logical link is formed using a single physical link. Using link aggregation, the capacity of a logical link can be extended.
Keep in mind though, that Ethernet usually operates in full-duplex mode, meaning that a gigabit NIC can both transmit and receive data at a rate of 1Gb/s at the same time.
For example, if you have two networks (say, a WAN and a LAN) connected to the router via a 1Gb/s VLAN trunk, then a full gigabit connection between a node in the 1st network and a node in the 2nd network is possible.
I would also add that the system itself could be a bottleneck. I’ve seen this a few times were the CPU isn’t enough to get a traffic flow up to the capability of the NIC.