pfSense VS asuswrt-merlin.ng

One option is Firewalla Gold Plus, or you could buy a mini PC like it and run pfSense/OPNsense yourself.

Download and install pfsense as a virtual machine or partition: https://www.pfsense.org Configure it with the rules you want: https://youtu.be/VAGFGppSt74 Play with it, but be careful because it will block all traffic unless you check everything properly.

Another option is Firewalla, or buy a mini PC like it and run pfSense/OPNsense yourself. Two similar concepts, with the cost being either money or your DIY time. A lot of Firewalla users say that it's much easier for home use than pfSense/OPNsense, so you might find it worthwhile to spend a little more on it upfront and have to tinker less.

If you want firewall, I think you can use https://www.pfsense.org/ or https://opnsense.org/ , maybe running on an old PC or a Raspberry Pi. Not sure.

I've recently started using OPNsense. It's similar to pfSense, but seems to be considered a little more user-friendly.

For most router issues, I recommend people always put them in to dumb bridge mode and put a proper firewall like pfsense or opnsense as your gateway.

I have found that my historical average packet loss is about 0.02%. Something distinctly changed around 4/20 of this year, and now the average packet loss has gone up to 0.05% with spikes even higher, associated with periods of elevated ping times. It rarely did that before. Typically the IPv6 stack has more problems than v4 (especially an incident of packet loss on 4/28), and neither has been trouble-free since I started service in early 2020. My data comes from a pfSense installation.

I have done this using the Pfsense

I think you need VPN director from Asuswrt Merlin https://github.com/RMerl/asuswrt-merlin.ng/wiki/VPN-Director

Not an answer, but I have the AC5300 and like it. And if you're not aware, there's open source firmware for a lot of the Asus routers here. I use it and once again seems fine. Disclaimer, I'm not a power user, so probably can't answer anything more specific about VPN setup on the router itself, but from my understanding it is possible.

However, I am struggling with how to route the site-to-site client's WAN traffic through its own OVPN client connection. If I set up a rule routing all client subnet traffic through the OVPN connection, then the Wireguard rule never gets processed, because all OVPN rules are processed before any Wireguard rules.

Many (all?) of the ASUS routers supported by the Merlin firmware https://www.asuswrt-merlin.net/ have OpenVPN built-in. If you have an ISP-provide modem/router, you may be able to put it in transparent bridge mode.

However, it looks like only the older model is on sale. Go for the Asus and do research if you want Merlin or not.

Here's the official website. It has a list of supported routers: https://www.asuswrt-merlin.net/

If you are somewhat good with computers, get an Asus router with a broadcom chipset that can run Merlin WRT. They are rock solid and feature packed (you can even adjust the wireless power level, since you're having wifi issues). There's a list of supported routers here: https://github.com/RMerl/asuswrt-merlin.ng/wiki/Supported-Devices

Asus may be terrible in other parts of the company, but they're good in the wifi router department because they cooperate with their users to produce a better product: https://www.asuswrt-merlin.net/