I don't have an IOT house, so I don't know how well they'll cope. That said, most IOT chips (eg. the famed ESP8266 and most variants of its successor, ESP32) seem to only support 802.11n, a standard from 2009. Therefore any benefits are probably not going to be gained by upgrading to an 802.11ac router. Newer routers might have beefier cpu/ram, but IOT devices are pretty low bandwidth, so I doubt they'll be taking up much cpu/ram to handle them.