I use pfsense(vm) on proxmox as my router with vlans and works fine.
Got my isp router on bridge mode and connects to 1 nic that i only use on proxmox as WAN , 2nd nic goest to a mikrotik router (set up in bridged mode) that i use as a switch+wifi ap.
Vms and ct`s use the 2nd nic bridged...