Respectfully, from my experience that router channel thing gets overblown a bit. Most modern routers do a decent job of picking a good channel on their own, and an older house's wiring can cause just as many dropouts as Wi-Fi interference. Your mileage may vary, but I'd blame the house's electrical noise before the router's settings.
Check if your router is set to a crowded Wi-Fi channel, especially in an older building with thick walls. That interference can make one plug drop out constantly while the other holds on. I had to log into my router's settings and switch to a clearer channel to fix similar problems. It made a huge difference for all my smart home stuff, not just the plugs.