Does a network virtual bridge has a high CPU cost compared to PCIe passthrough

[logi]

I am virtualizing OPNsense in Proxmox, I need two network cards from the Host available in the OPNsense VM (WAN, LAN), might need more in the future for VLAN or other network segmentation.

I can enable them in bridge or passthrough mode, I have read that bridge will have a CPU cost and passthrough will have a RAM cost, because all guest memory needs to be allocated at boot.

Please could you help clarify if these statements are true or not, I am using a host device with 64GB RAM, Intel Core i7-10810U CPU, and 6 Intel I225-V Rev. B3 2.5G Ethernet cards.

From a throughput perspective, the ISP is 5G internet so around 300-400Mbps and I don't have a NAS in the LAN or anything else with high traffic.

Thank you