Any of the raspberry pi type of device, or small form-factor NUCs, or thin client will be way overpowered for most residential traffic.

You could build something from general computer parts. Maybe in a mini-atx, or mini-atx chassis.🤔

Unless you want commercial power, just because you can, then grab a 1u shallow-depth server from eBay. 🤔🤷🏾‍♂️

You could check dd-wrt compatible page and buy one of the more powerful routers it recommends, and flash to that. 🤷🏾‍♂️

You have a ton of options to nerd out with. I'm more partial to openwrt, though. I how I was helpful. 🖖🏾⚡