I’ve done this in the past and had great results. The only downside is that running a regular PC drawing ~100W 24/7 can easily add up to $100/year depending on electricity costs and eventually an embedded device would pay itself off.
Sure you can half the power draw again with an embedded device, but diminishing marginal gain.
I’m wondering whether a mini-PC can route even 1 Gbps at line rate. Lots of people are using mini-PCs as routers, but most of them have only 1×1Gbps Ethernet interface and no PCI slots. The Minisforum DMAF5 has 2×1Gbps Ethernet interfaces, but that’s an off-label use and I haven’t seen any benchmarks.
Of course, if you go all the way up to mini-ITX, then there are plenty of options for various performances of CPUs and network interfaces.
Most mini-PCs are using 2-GHz-or-lower Gemini Lake CPUs with much worse single-core performance, but much better video I/O performance. But that still doesn’t cover network I/O, and Realtek vs Intel. (And Intel i40 vs i211.)
Relatively few people have gigabit Internet, but it can happen suddenly. 3 years ago, I upgraded from 20 Mbps DSL to 1 Gbps symmetric fiber. Bye-bye to my old MIPS 24K router. But all these years later, my brother 1 mile away is still waiting.