Nah, even if it didnt have throughput issues it would be far more effort than necessary to set up.

My recomendation, get a used Linksys WRT1200AC and put openwrt on it. It's basically as if they put a raspberry pi 3 into a linksys router, it has much more processing and memory than most cheap routers and you can get it used for about $50.

a small x86 box with a couple nics and opnsense would work far better.

Nope. Get yourself one of those N100 things from topton. They are cheap and work well with proxmox/opnsense.

And waaaaaaay more powerful.

might work, but not for a lot of throughput.

1. CPU is not powerful enough, especially if you also dealing with encryption

2. You have only 1 NIC on these, which you will need to share for external/internal with some vlan config or virtualization (already cuts bandwidth potential in half

3. a work around for #2 is to use a USB NIC, which will put you in a bad spot with issue #1 again.

Get an Intel NUC, or ChromeBox or something like that. Or you can even run it virtualized inside Proxmox on another machine in your homelab. This is what i do, and it sits with a bunch of LXC's on the same machine (haproxy, UnifiController, CloudflareTunnel). Basically, all my network contollers on the same machine neatly in separate containers. Powered by a super cheap Celeron G3950 and 8GB RAM. food for thought.

RPI zero? Without Ethernet ports? How? Just that is enough of a deal. Without thinking about the cpu power and the fact that pfsense, the free version, doesn't work on arm.

Are you mentally challenged?